LIBRARY 


UNIVERSITY  OF  CALIFORNIA 
Deceived          /  /  Ltf  /7     . 


^Accessions 


THE   PRINCIPLES 


OF 


MODEM  DAIRY  PRACTICE 

.  FROM  A 

BACTERIOLOGICAL  POINT  OF  VIEW. 


BY 

GOSTA   GROTENFELT, 

President  Mustiala  Agricultural  College,  Finland. 


AUTHORIZED  AMERICAN  EDITION 

BY 

F.   W.  WOLL, 

Assistant  Professor  of  Agricultural  Chemistry,  University  of  Wisconsin 


'Hi)  KHustrations. 


FIRST 

FIRST  THOUSAND. 


NEW  YORK: 

JOHN    WILEY   &    SONS, 
53  EAST  TENTH  STREET. 

1894. 


Copyright,  1894, 

BY 

F.    W.  VVOLL. 


PREFACE  TO  AMERICAN  EDITION. 


IT  is  doubtful  whether  any  industry  has  changed  more 
during  the  past  twenty  years  than  has  that  of  the  produc- 
tion of  milk  and  its  manufacture  into  butter  and  cheese. 
Progress  has  been  made  in  every  direction.  The  present 
generation  has  seen  the  shallow-setting  system  of  cream- 
raising  superseded  by  the  deep-setting  systems,  and  these 
again  largely  by  hand  or  power  separators.  The  wonderful 
growth  of  the  creamery  movement,  the  invention  of  the 
cream-separator  and  the  butter-extractor,  the  introduction 
of  pure  cultures  in  the  manufacture  of  butter,  have  all 
come  to  us  during  this  time,  as  have  also  the  various 
methods  of  preserving  milk  for  direct  consumption;  and 
still  more,  underlying  it  all,  an  increased  knowledge  has 
been  gained  and  a  fuller  understanding  of  the  nature  and 
properties  of  dairy  products  and  the  changes  to  which  they 
are  subject. 

In  this  advance  of  the  dairy  industry  the  Scandinavian 
countries  have  taken  the  most  prominent  part,  Denmark 
and  Sweden  having  given  the  cream-separator  to  the 
world — the  former  country  also  contributing  the  method 
of  ripening  cream  by  means  of  pure  cultures,  and  the 
latter  the  butter-extractor.  Also  Finland — Scandinavian 
by  language,  if  not  by  government — has  contributed  her 
share  to  the  advancement  of  dairying;  and  for  a  long  time 

iii 


IV  PREFACE   TO   AMERICAN    EDITION. 

past  large  quantities  of  "  gilt-edged "  butter  have  every 
year  found  their  way  from  her  distant  borders  to  the  large 
markets  of  the  world. 

The  author  of  this  book  is  well  known  to  Scandinavian 
dairymen  from  his  numerous  and  important  publications  on 
dairy  subjects;  and  in  the  broader  field  of  science,  which 
knows  no  boundary  of  nationality  or  language,  his  investi- 
gations relating  to  milk  have  made  his  name  familiar  to 
students  of  dairying  and  bacteriology.  A  study  of  the 
present  work  will,  I  think,  show  the  reader  that  it  is  writ- 
ten by  a  thorough  scholar,  closely  acquainted  with  all  the 
different  operations  of  the  dairy. 

The  work  has  been  revised  by  the  author  at  my  sug- 
gestion, and  several  additions  have  been  made — e.g.,  the 
whole  of  Part  V,  on  "  Cheese."  It  has  been  my  effort  in 
preparing  the  translation  to  make  it  directly  applicable  to 
our  methods  of  dairying.  It  was  therefore  found  necessary 
to  edit  the  original  in  places  to  adapt  it  to  the  changed 
conditions.  Numerous  explanatory  foot-notes  and  refer- 
ences have  been  added,  which  I  trust  will  prove  of  value 
to  the  student  of  dairying  and  dairy  bacteriology  without 
detracting  from  the  value  of  the  book  to  the  practical 
dairyman.  I  have  endeavored  to  include  all  recent  Ameri- 
can and  European  work  in  this  line  in  my  additions,  so  as 
to  make  the  record  of  the  investigations  complete. 

I  wish  to  acknowledge  the  assistance  of  Dr.  H.  L. 
Russell,  Assistant  Professor  of  Bacteriology  of  this  Uni- 
versity, in  preparing  the  translation.  Dr.  Russell  has  also 
kindly  furnished  me  with  several  valuable  additions  giving 
the  results  of  original  investigations. 

F.  W.  WOLL. 
MADISON,  WISCONSIN. 


TABLE  OF  CONTENTS. 


PAGE 

INTRODUCTION:  BACTERIA  AND  THEIR  RELATION  TO  DAIRYING       1 


PART  I.— MILK. 

CHAPTER 

I.  Milk  as  Drawn  from  the  Udder 23 

II.  Sources  of  Infection  in  the  Stable,  and  its  Prevention      .  26 

III.  The  Common  Forms  of  Bacteria  found  in  Cows'  Milk      .  80 

IV.  Cleanliness  in  Butter  and  Cheese  Factories 108 

V.  Milk  for  City  Consumption 137 

VI.  Sterilization  of  Milk 144 

VII.  Pasteurization  of  Milk 157 

PART  II.-CREAM. 

I.  Cream  Raised  by  Gravity  Processes 166 

(a)  The  Old  Shallow-Setting  System  .......  166 

(b)  The  Modern  Systems  of  Gravity  Creaming      .     .     .  175 
II.  Separator  Cream     . 181 

PART  III.— SKIM  MILK 

(a)  Skim-milk  from  Gravity  Creaming 193 

(b)  Separator  Skim-milk 196 

(c)  Pasteurization  of  Skim-milk 196 


VI  TABLE   OF    CONTENTS. 


PART  IV.— BUTTER. 

CHAPTER  PAGE 

I.  Treatment  of  Creain  Previous  to  the  Churning  .     .     .     .  204 

(a)  Sweet-cream  Butter.     "Paris  Butter " 205 

(b)  Sour-cream  Butter 207 

(c)  The  Use  of  Pure  culture  Acid  Starters 220 

II.  Manufacture  and  Handling  of  Butter    .......  237 

III.  Diseases  of  Butter .     .     .     .     .  252 

PART  V.— CHEESE 

I.  Bacteria  and  Cheese-making 258 

II.  Old-method  Cheese-making 270 

III.  New-method  Cheese-making 274 

INDEX  .                                                                      .  279 


MODERN  DAIRY  PRACTICE, 


INTRODUCTION. 
BACTERIA  AND  THEIR  RELATION  TO  DAIRYING. 

' '  Dairying  is  an  art  the  success  of  which 
depends  almost  entirely  on  the  extent  to  which 
we  succeed  in  controlling  the  various  fermen- 
tation processes  in  their  course." 

— ERNST  KRAMER. 

THE  great  importance  of  bacteria  in  the  dairy  industry 
is  at  present  admitted  by  all  who  have  given  the  subject  any 
thought.  A  knowledge  of  the  nature  and  characteristics 
of  these  minute  organisms  will  help  us  to  understand  more 
thoroughly  the  various  manufacturing  processes  of  the 
dairy  and  will  throw  light  on  problems  that  often  perplex 
the  dairyman.  Since  the  changeable  nature  of  dairy 
products  makes  it  especially  desirable  to  study  all  means 
at  our  disposal  in  order,  if  possible,  to  increase  their  keep- 
ing quality,  an  inquiry  into  the  influence  of  trie*  bacteria  in 
the  dairy  will  be  of  the  highest  value  to  the  practical 
dairyman  and  to  all  who  handle  milk  and  milk  products. 
It  will  teach  us  not  only  to  produce  goods  that  will  keep 
well,  but  to  care  for  them  afterwards  so  that  they  do  not 
prematurely  spoil. 


2  MODERN   DAIRY   PRACTICE. 

Before  proceeding  to  the  consideration  of  these  problems 
it  will,  however,  be  necessary  to  give  some  general  informa- 
tion concerning  bacteria  and  their  prominent  characteristics 
of  life,  so  that  the  reader  will  be  able  to  follow  the  discus- 
sions entered  upon  in  the  main  part  of  this  work. 

Bacteria. — Bacteria  are  the  tiniest  forms  of  organic  life 
known;  they  are  single  cells  belonging  to  the  lowest  type 
of  plant  life. 

They  vary  somewhat  in  form  and  there  is  considerable 
difference  in  size.  The  different  species  of  bacteria  cannot 
be  distinguished  by  their  form  and  shape  as  with  the 
higher  order  of  plant  or  animal  life,  because  so  many  of 
them  have  such  strong  similarities  in  this  respect.  The 
usual  method  of  classifying  them,  which  is  admitted  to  be 
imperfect,  bases  the  distinguishing  characters  entirely  upon 
shape. 

There  are  three  fundamental  types  known,  that  may 
be  compared  in  shape  to  a  ball,  a  short  rod,  and  a  cork- 
screw. These  three  types  are  called  (1)  coccus,  (2)  ba- 
cillus, and  (3)  spirillum.  All  forms  of  bacteria  may  be 
referred  to  these  three  fundamental  types,  although  there 
are  gradations  between  them.  Other  names  are  given  to 
certain  species  on  account  of  the  way  in  which  the  indi- 
vidual cells  may  be  joined  to  each  other:  i.e.,  if  the  cell  is 
isolated  it  is  called  a  micrococcus;  two  coccus  forms  joined 
closely  are  spoken  of  as  diplococcus.  Sometimes  the  cells 
may  adhere  in  long  chains  and  are  then  known  as  strepto- 
coccus. If  they  form  clusters  instead  of  chains  they  are 
called  staphylococcus.  A  few  coccus  forms  grow  out  in  a 
platelike  expansion,  when  they  are  called  tetrads.  If  they 
multiply  in  three  directions  of  space  instead  of  in  two 
they  form  cubical  masses  known  as  saroina. 


BACTERIA   AND   THEIE   RELATION  TO   DAIRYING. 


The  bacilli  include  the  elongated  rodlike  cells.  They 
vary  greatly  in  length  and  are  sometimes  divided  into  sub- 
divisions, such  as  bacterium,  meaning  a  short  cell  devoid 


Fig.  1,  micrococci  ;  Fig.  2,  diplococci :  Fig.  3,  streptococci  ;  Fig.  4,  tetrads; 
Fig.  5,  sarcina  ;  Fig.  6,  bacilli  ;  Fig.  7,  comma  bacilli  ;  Fig.  8,  spirilli ;  Fig.  9, 
yeast  fungi;  Figs.  10  and  11,  bacilli  with  spores  ;  Fig,  12,  bacilli  with  cilia,— 
all  highly  magnified. 


4  MODERN   DAIRY  PRACTICE. 

of  any  spore-bodies  within;  bacillus,  the  normal  rodlike 
type,  reproducing  by  spores  tinder  certain  conditions;  and 
leptotliorix,  where  the  filaments  are  extremely  long  and 
slender. 

The  spirilla  are  the  curved  forms,  and  vary  most  in 
their  outward  appearance.  They  may  be  merely  undulat- 
ing in  appearance  or  in  segments  merely  curved,  when  they 
are  sometimes  spoken  of  as  vibrios.  To  this  class  belongs 
the  cholera  germ,  often  called  the  comma  bacillus  on  account 
of  its  curved  appearance.  Many  times  the  spirilla  are 
curved  into  several  sharply-defined  turns. 

Size  and  Weight  of  Bacteria. — As  already  mentioned 
the  bacteria  vary  much  in  size,  for  which  reason  it  is  im- 
possible to  give  their  average  dimensions.  A  couple  of 
examples  will  convey  some  idea  of  their  extraordinary 
minuteness. 

A  common  lactic-acid  bacterium  is  generally  3  micro- 
millimeters  long  and  1  micromillimeter  wide.  One  micro- 
millimeter  (jj)  is  y^Vrr  millimeter  or  3-5 -J  or  °f  one  inch. 
How  exceedingly  small  must  not,  then,  the  organisms  be, 
25,000  of  which  may  be  placed  side  by  side  without  span- 
ning over  more  than  an  inch !  Not  less  than  10,000  million 
single  bacteria  would  be  needed  to  fill  a  cubic  millimeter. 
Their  weight  is  also  exceedingly  small.  If  we  assume  that 
the  specific  gravity  of  the  bacterium  mentioned  is  equal  to 
that  of  the  water  (this  may  not  be  exact,  but  is  not  very 
much  out  of  the  way)  it  weighs  a  little  over  .0000000001 
milligram;  and  something  over  900  billions  of  such  or- 
ganisms are  required  to  reach  a  weight  of  1  gram  (^  of  an 
ounce). 

Distribution  of  Bacteria. — It  is  evident  that  such  small 
organisms  may  hide  everywhere  in  nature.  They  have 


BACTERIA   AND   THEIR   RELATION   TO   DAIRYING.          5 

been  found  in  air,  soil,  water,  dust;  on  our  clothes,  on  our 
skin;  in  the  alimentary  canal  of  man  and  animals,  in  our 
food;  on  the  trees  and  the  flowers,  on  the  smallest  as  well 
as  the  largest  animals, — in  short,  in  almost  every  place  on 
earth.  Among  the  few  exceptions  to  the  omnipresence  of 
bacteria  may  be  mentioned  that  they  are  never  found  in 
the  uninjured  animal  and  vegetable  cells  or  in  fresh, 
unwounded  animal  and  vegetable  organs.  Their  won- 
derful general  distribution  is  due  largely  to  their  exceed- 
ingly small  weight ;  they  are  easily  carried  around  in  the 
air,  and  when  dry  are  moved  by  the  least  current.  Certain 
bacteria  furthermore  possess  power  of  locomotion  in  the 
fluids  adapted  to  their  development,  and  they  can  therefore 
spread  in  these  substrata  with  wonderful  rapidity. 

Multiplication  of  Bacteria.— The  main  reason  of  the 
universal  presence  of  bacteria  is,  however,  not  to  be  found 
in  any  of  the  conditions  mentioned,  but  in  their  enor- 
mously rapid  reproductive  capacity.  This  takes  place 
partly  by  division,  partly  by  spores. 

a.  Multiplication  by  Division. — Bacteria  may  divide  in 
different  ways.  The  most  common  method  is  by  the  sim- 
ple division  of  a  single  cell-element  into  two  equal  parts 
(fission).  This  may  continue  in  a  linear  direction,  giving 
rise  to  long  threads  or  chains  of  cells.  In  the  case  of  coccus 
forms  the  continued  division  into  twos  may  give  rise  to 
the  streptococci  (chain  cocci) ;  or,  if  irregular  and  in  two 
planes,  it  may  form  flattened  surfaces  or  launches— pus 
bacteria. 

If  division  occurs  in  three  planes  we  have  the  formation 
of  the  cubical  masses  or  sarcina  groups. 

Under  favorable  conditions  the  multiplication  through 
division  may  take  place  very  rapidly.  It  has  been  observed 


6  MODERN   DAIRY    PRACTICE. 

in  case  of  some  bacteria  that  the  time  elapsing  between  the 
division  of  the  mother  bacterium  and  the  moment  when 
the  new  bacterium  in  its  turn  begins  to  multiply  amounts 
to  only  twenty  minutes.  As  a  rule  the  interval  may  not 
be  as  short,  but  it  often  does  not  amount  to  more  than 
about  an  hour.  A  bacterium  which  grows  and  divides 
into  two  organisms  during  this  time  may,  under  ideal  con- 
ditions, within  24  hours  be  the  ancestor  of  16,777,214  or- 
ganisms. A  sarcina  which  produces,  e.g.,  eight  new  bac- 
teria in  an  hour  by  dividing  in  three  directions,  may  after 
20  hours  have  an  offspring  so  enormous  that  it  is  1,111,- 
152,347  times  larger  than  the  number  of  human  beings 
found  on  our  planet;  the  figure  indicating  the  number  of 
this  progeny  would  contain  nineteen  ciphers  I 

As  a  corollary  of  this  enormously  rapid  multiplication 
it  follows  that  the  bacteria  in  general  must  exist  in  nature 
under  highly  unfavorable  conditions,  as  they  would  other- 
wise soon  fill  the  whole  earth  and  annihilate  everything 
else  living. 

5.  Multiplication  ~by  Spores.  —  The  multiplication 
through  spores  (Figs.  10-11)  occurs  in  the  manner  that 
small  round  or  egg-shaped  bodies  with  a  characteristic 
power  of  refraction  are  formed  within  the  bacterium,  and 
later  on  these  grow  to  ordinary  bacteria,  under  proper  condi- 
tions of  heat  and  moisture.  The  spores  possess  far  greater 
power  of  resistance  against  drought,  heat,  cold,  etc.,  than 
do  the  bacteria  themselves.  The  fact  that  these  often 
prove  almost  indistinguishable  from  the  material  to  which 
they  have  once  gained  access  depends  in  most  instances 
on  the  fact  that  spores  have  been  formed  there.  If,  e.g., 
sporeless  bacteria  dry  up,  they  die  comparatively  soon, 
within  a  day,  or  perhaps  a  week.  If  the  conditions  are 


BACTERIA   AND   THEIR   RELATION   TO    DAIRYING.  7 

not  too  unfavorable,  the  spores,  on  the  other  hand,  may 
often  continue  to  live  for  years  after  the  nutritive  solution 
has  died  out.  It  must  be  noted,  however,  that  there  are 
exceptions  to  the  rule  in  both  cases.  The  spores  are  far 
less  susceptible  to  changes  in  temperature  than  the  bac- 
teria themselves.  While,  e.  g.,  sporeless  bacteria  generally 
are  killed  under  favorable  conditions  within  about  ten 
minutes,  when  exposed  to  a  moist  heat  of  158°-176°  F. 
(70°-80°  C.),  the  spores  of  several  species  survive  after  hav- 
ing been  exposed  even  to  live  steam  for  hours.  The  spores 
of  a  certain  potato  bacillus  can  stand  this  treatment  for 
almost  six  hours  without  succumbing.  A  large  number 
of  spores  are  not  killed  except  by  dry  heat  at  266°-284°  F. 
(130°-140°  C.).  We  thus  find  among  the  spores  of  bacteria 
some  of  the  most  tenacious  organisms  in  the  vegetable  or 
the  animal  world. 

Some  bacteria  (above  all  a  large  number  of  bacilli)  are 
supplied  with  fine  cilia  (Fig.  12),  and  have  under  favorable 
external  conditions  a  lively  power  of  locomotion. 

Pathogenic  and  Non-pathogenic  Bacteria. — Some  bac- 
teria have  become  known  and  feared  from  their  power  of 
producing  infectious  diseases  in  the  animal  body.  Owing 
to  this  fact,  everything  known  by  the  name  of  bacteria 
has  been  the  object  of  fear  and  suspicion  to  most  peo- 
ple. This  is,  however,  without  any  foundation.  By  far 
the  larger  number  of  bacteria  are  not  disease-producing 
and  are  not  injurious  to  the  animal  organism.  Some  of 
the  harmless  majority  distinguish  themselves  by  the  fact 
that  they  call  forth  fermentation  in  all  kinds  of  fermenta- 
ble fluids,  while  others,  as  far  as  known  to  modern  science, 
are  entirely  indifferent. 

In  these  studies  and  investigations  we  shall  first  of  all 


8  MODERN   DAIRY   PRACTICE. 

consider  the  bacteria  producing  fermentations.  For  this 
reason  the  following  short  account  of  the  conditions  of 
life  of  bacteria  holds  good  primarily  in  case  of  this 
group. 

Nutrition  of  Bacteria. — The  bacteria  are  usually  ex- 
ceedingly unpretentious  in  their  demands  for  the  good 
things  of  life,  a  fact  which,  of  course,  is  one  of  the  main 
reasons  for  their  universal  distribution  in  nature.  The 
smallest  quantities  of  organic  matter  are  sufficient  for 
their  support  ;  and  wherever  they  find  such  a  substance 
which  possesses  the  moisture  and  heat  necessary  for  their 
development  and  a  reaction  favorable  to  their  activity, 
they  will  grow  and  multiply  there. 

The  bacteria  live  on  the  ready-formed  carbonaceous 
compounds  of  organic  origin,  and  do  not  as  a  rule  possess 
the  ability  to  make  use  of  carbonic  acid.  The  different 
species  of  bacteria  usually  select  different  kinds  of  carbo- 
hydrates. Some  thrive  best  when  the  nutritive  solution 
contains  grape-sugar  ;  others  when  it  contains  cane-sugar 
or  milk-sugar,  etc.  Hence  we  find  that  the  different 
nutritive  substances  often  are  contaminated  with  their 
own  peculiar  kinds  of  bacteria.  Only  a  few  bacteria  are 
omnivorous  and  satisfied  with  almost  any  organic  sub- 
stratum. 

The  nitrogen  in  the  nutritive  substratum  required  by 
the  bacteria  may  be  obtained  not  only  from  organic  sub- 
stances, but  from  certain  inorganic  materials,  like  nitric  acid 
and  ammonia  compounds.  The  bacteria,  however,  usually 
prefer  albuminoids.  Very  few  bacteria  can  do  entirely 
without  nitrogeneous  substances.  The  need  of  the  dif- 
ferent species  of  nitrogen  varies  greatly.  The  bacteria 
living  mainly  on  carbohydrates  need  only  very  minute 


BACTERIA  AND   THEIR   RELATION   TO   DAIRYING. 

quantities  of  nitrogen  for  their  development,  while  a 
high  nitrogen  content  in  the  substratum  is  an  absolute 
condition  of  life  with  others.  As  regards  the  need  of 
bacteria  of  salts  (mineral  matter)  they  behave  usually  like 
ordinary  fungi.  It  must  be  especially  noted  that  alkali 
salts  are  very  important  for  the  nutrition  of  bacteria. 

Bacteria  and  Moisture. — Not  only  the  chemical  com- 
position of  the  substratum :  but  also  the  degree  of  moisture 
in  the  same  is,  as  already  mentioned,  of  importance  for 
the  development  of  bacteria.  Organic  life  is  inconceiva- 
ble without  a  certain  content  of  moisture  in  the  nutritive 
substratum.  We  saw  above  that  sporeless  bacteria  die 
comparatively  rapidly  in  the  absence  of  moisture,  while 
the  spores,  on  the  other  hand,  retain  their  power  of  life 
even  a  long  time  after  the  substratum  is  completely  dried 
out. 

Bacteria  and  Heat. — Heat,  this  mighty  spring  in  the  ma- 
chinery of  organic  nature,  is  also  of  great  importance  for 
bacteria,  although  the  various  species  have  very  different 
demands  in  this  respect.  It  may  be  said  in  general  that 
39°  F.  (4°  0.)  is  the  lowest  temperature  at  which  bacteria 
can  multiply  and  grow.  Below  this  temperature  they  fall 
into  a  torpor  from  which  they  are  awakened  only  by  in- 
creasing temperature. 

"With  most  bacteria  the  torpor-like  condition  appears 
even  before  this  temperature  has  been  reached.  Some 
species  have  been  found  in  ocean  water  and  in  the 
soil,  however,  which  can  multiply  even  at  0°.  While 
the  development  of  bacteria  is  arrested  by  a  low  tem- 
perature, a  large  number  of  them  are  able  to  stand  intense 
cold  without  being  destroyed.  The  bacteria  of  splenic 
fever  are  said  to  live  even  after  having  been  subjected  to 


10  MODERK   DAIRY   PRACTICE. 

a  cold  of  —166°  F.  (  —  110°  C.)  for  an  hour,  a  temperature 
which  only  few  organisms  can  stand  ;  the  cholera  bacteria 
can  stand  a  cold  of  14°F.  (  —  10°  C.)  for  the  same  length  of 
time  without  being  destroyed;  and  typhus  bacteria  have 
been  known  to  remain  alive  for  100  days  frozen  in  the  ice. 
A  special  account  is  given  later  on  of  the  influence  of  cold 
on  certain  fermentation  bacteria. 

It  is,  however,  not  only  cold  but  also  high  heat  which 
arrests  the  development  and  multiplication  of  bacteria. 
Temperatures  between  39°  and  122°  F.  (4°  and  50°  C.)  are 
most  favorable  to  their  development.  At  140°-158°  F.  (60°- 
70°  C. )  their  vegetative  forms  are  usually  killed,  provided 
this  temperature  is  allowed  to  act  for  a  sufficiently  long 
time,  while  the  spores  can  stand  a  much  higher  heat. 
The  optimum  temperature,  i.e.,  the  most  favorable  tem- 
perature, for  the  development  of  the  pathogenic  bacteria 
(the  disease  bacteria)  coincides  nearly  with  the  body  tem- 
perature of  animals;  for  the  greater  portion  of  the  other 
bacteria  and  especially  for  the  fermentation  bacteria  it  is 
from  59°-77°  F.  (15°-25°  C.).  There  are,  however,  num- 
erous exceptions  to  these  rules.  There  are  thus,  e.g.,  some 
soil  and  water  bacteria  which  only  develop  at  122°-158°  F. 
(50°-70°  C.).  I  have  further  found  bacteria  in  milk  that 
were  not  only  alive  but  multiplied  at  140°-149°  F.  (60°-65° 
C.).  At  lower  temperatures  the  development  of  these  bac- 
teria was  practically  suspended. 

Chemical  Reaction  Necessary  for  Baetsria, — The  develop- 
ment of  bacteria  also  depends  on  the  chemical  reaction  of 
the  nutritive  substratum.  An  alkaline  or  at  least  a  neutral 
reaction  is  an  essential  condition  for  a  large  majority. 
Some  few  bacteria  can,  on  the  other  hand,  thrive  in  an 
acid  substratum,  (e.g.,  lactic-acid  bacteria).  An  acid  re- 


BACTERIA   AKD   THEIR  RELATION   TO   DAIRYING.        11 

action  of  the  nutritive  substratum  is  especially  favorable  to 
the  development  of  the  moulds. 

Finally,  two  factors  must  here  be  noted  which  have  the 
greatest  influence  on  bacterial  life,  viz.,  air  and  light. 

Bacteria  and  the  Air. — A  large  number  of  bacteria  are 
entirely  dependent  on  the  oxygen  of  the  air,  and  perish  if 
they  do  not  have  access  to  the  same.  These  are  called 
aerobic  bacteria.  On  the  other  hand,  oxygen  acts  as  a 
poison,  or  at  least  as  a  narcotic,  to  other  forms  (ana- 
erobic bacteria).  Some  bacteria  can  further  exist  both 
in  an  atmosphere  of  oxygen  and  in  its  absence.  Many  of 
the  latter  organisms  differ  in  behavior  according  to 
whether  they  have  access  to  air  or  not. 

Bacteria  and  Light. — The  large  majority  of  bacteria 
like  total  darkness,  and  only  a  few  thrive  in  direct  light. 
Direct  sunshine  as  a  rule  acts  as  a  poison  on  all  organisms 
included  under  the  term  bacteria;  and  if  ordinary  day- 
light is  allowed  to  act  on  them  for  a  sufficiently  long  time 
and  with  proper  intensity,  not  only  most  of  the  vegetative 
forms  but  even  their  spores  will  be  destroyed.  Sunlight 
is  therefore  the  most  common,  the  cheapest,  and  the  most 
effective  means  at  our  disposal  of  fighting  the  bacteria. 
Light  exercises  its  power  of  destruction  of  bacteria  on  a 
large  scale.  In  nature  the  destruction  is  most  intense 
during  the  summer  months.  A  putrefactive  liquid,  the 
condition  of  which,  as  is  well  known,  is  due  to  a  fermen- 
tation brought  about  by  bacteria,  can  even  become  sterile 
through  the  action  of  sunlight  alone.  The  more  generous 
the  supply  of  air  while  the  bacteria  are  exposed  to  the 
sunlight,  the  more  rapidly  they  and  their  spores  are 
destroyed. 

Bacteria  and  Disinfectants. — It  must  furthermore  be 


12  MODEKH   DAIRY   PRACTICE. 

stated  as  a  characteristic  of  bacteria,  as  well  as  of  all  other 
living  organisms,  that  they  shun  certain  chemicals  which 
either  arrest  their  growth  or  entirely  destroy  them.  These 
materials  are  called  either  disinfectants  or  antiseptics. 
Further  information  concerning  the  disinfectants  especially 
adapted  for  use  in  dairy  practice  will  be  found  later  on  in 
this  work. 

Bacteriological  Methods  of  Investigation. — We  cannot 
here  enter  into  a  detailed  account  of  bacteriological  meth- 
ods of  investigation.  It  may  be  proper,  however,  to  explain 
briefly  the  nature  and  general  characteristics  of  these 
methods,  in  order  that  the  discussions  entered  upon  in  the 
body  of  this  book  may  be  more  easily  understood  by  per- 
sons not  familiar  with  bacteriological  science.  Those  in- 
tending to  study  in  a  more  systematic  manner  the  rela- 
tions dwelt  on,  are  referred  first  of  all  to  the  splendid 
text-books :  C.  J.  Salomonsen's  "  Bakteriologisk  Teknik  for 
Mediciner,"  published  in  1889,  and  Hueppe's  comprehen- 
sive work,  "  Die  Methoden  der  Bakterienforschung,"  1889. 
An  interesting  and  plain  presentation  of  the  subject  is 
given  in  the  Swedish  language  in  Prof.  Curt  Wallis'  book, 
"  Bakteriologi "  (1888).* 

*  The  following  is  a  list  of  the  more  important  works  on  Bac- 
teriology in  the  English  and  German  languages,  besides  those  men- 
tioned above: 

STERNBERG.    Manual  of  Bacteriology.     New  York,  1892. 

ABBOTT.     Principles  of  Bacteriology.     Philadelphia,  1892. 

FRANKEL.  Text-book  of  Bacteriology,  tr.  by  Linsley.  New 
York,  1891. 

MIGULA.     Practical  Bacteriology.     London,  1893. 

JORGENSEN.  The  Micro-Organisms  of  Fermentation.  London, 
1893. 

WOODHEAD.    Bacteria  and  their  Products.    London,  1892. 


BACTERIA   AND   THEIR   RELATION   TO   DAIRYING.        13 

Three  methods  are  generally  used  in  the  study  of  bac- 
teria, viz.:  (a)  microscopic  examination;  (b)  culture  of  the 
bacteria  on  different  nutritive  substrata;  and  (c)  inocula- 
tion experiments  with  animals.  As  we  are  here  dealing 
especially  with  non-pathogenic  bacteria,  we  shall  only 
dwell  on  the  first  two  methods,  since  inoculation  is  only 
used  in  the  study  of  pathogenic  bacteria. 

a.  Microscopic  Examination. — In  applying  the  first 
method,  a  compound  microscope  is  essential.  This  ought 
to  magnify  at  least  500  times,  and  preferably  more.  With 
such  an  instrument  the  presence  of  bacteria  can  be  directly 
proved  in  several  liquids,  as  in  case  of  slops  from  creamery- 
gutters,  standing  liquid-manure  pools,  etc.  In  other  liq- 
uids and  in  mediums  where  the  bacteria  present  either  ap- 
pear in  smaller  numbers  or  are  extremely  small  or  are 
hidden  by  other  bodies  (as  in  the  cream  and  milk)  they 
cannot  be  observed  in  this  easy  manner.  In  such  cases 
the  bacteria  must  be  stained, — an  operation  usually  per- 
formed by  means  of  different  anilin  colors, — and  they  will 
then  appear  plainly  when  seen  through  a  microscope. 
Although  this  method  in  many  instances  will  lead  to  im- 
portant observations,  it  seldom  gives  decisive  results  as 
regards  the  question  of  the  characteristics  of  single  species. 
The  bacteria  are  extremely  simple  organisms,  which  offer 

KRAMER.    Die  Bakteriologie  in  ihren  Beziehung  zur  Landwirt- 

schaft,  Wien,  1892. 
FREUDENREICH.    Bakteriologie  in  der  Milchwirtschaft.    Basel, 

1893. 

GfJNTHER.    Bakteriologie.    Leipzig,  1890. 
CONN.     The  Fermentations  of  Milk.    Washington,  1892. 
WEIGMANN.    Die  Methoden  der  Milchconservirung.     Bremen, 

1893.  W. 


14  MODERN   DAIRY   PRACTICE. 

but  few  dissimilarities  in  their  outward  appearance.  There 
are,  e.g.,  a  large  number  of  species  among  the  micrococci 
which  appear  entirely  similar  by  examination  with  a  micro- 
scope, but  which  show  great  differences  in  their  effects  and 
general  behavior  in  one  and  the  same  substratum,  and  thus 
indicate  beyond  a  doubt  that  they  are  in  reality  different 
species.  It  has  therefore  been  found  necessary  to  seek  a 
more  certain  method  of  identification  than  the  microscopic 
examination,  and  such  a  one  has  also  been  found  in  the 
culture  method. 

b.  Culture  Method  of  Bacteria  Investigation. — Bacteria 
can  develop  in  several  kinds  of  media,  both  liquid  and 
solid.  In  the  former  they  form  all  kinds  of  flocculent  and 
sandy  growths,  while  in  the  latter  they  grow  into  more  or 
less  characteristic  isolated  masses,  technically  called  colo- 
nies. In  the  culture  of  bacteria  for  scientific  objects  French 
bacteriologists  previously  used  mainly  liquid  substrata  and 
German  preferably  solid  ones.  Both  kinds  are  of  late  made 
use  of  by  all  bacteriologists.  The  liquid  nutritive  media  dis- 
tinguish themselves  by  the  fact  that  the  conditions  which 
they  offer  to  the  bacteria  resemble  those  found  in  nature, 
and  that  all  kinds  of  fermentations  may  be  more  easily 
observed  in  them;  the  solid  substrata,  on  the  other  hand, 
are  the  more  convenient  ones  to  use  when  the  question  of 
the  specific  growth  of  different  species  is  studied.  Among 
the  liquid  substrata  used  in  bacterial  investigations  may  be 
mentioned  beef-broth,  milk,  malt-extract,  sugar  solutions 
prepared  in  different  ways,  and  extracts  of  various  fruits; 
among  the  solid  nutrients,  prepared  potatoes  and  beef -tea, 
to  which  pepton  and  all  kinds  of  gelatinizing  substances 
have  been  added,  as  gelatine,  agar-agar,  etc.  Coagulated 
blood-serum  and  soaked  wheat-bread  are  also  often  used. 


BACTERIA   AND   THEIR   REEATION   TO   DAIRYING.        15 

Sterilization  of  Culture  Media. — When  these  nutritive 
media  are  used  for  the  culture  of  bacteria  they  must  be 
sterile,  i.e.,  free  from  all  living  organisms,  as  the  culture 
would  otherwise  be  impure  from  bacteria  found  in  the  sub- 
stratum before  the  organism  to  be  studied  was  seeded  or 
inoculated  in  it.  Sterilization  is  usually  effected  by  heat- 
ing to  such  a  temperature  that  both  bacteria  and  their 
spores  are  killed.  As  we  saw  in  the  preceding,  the  vitality 
of  different  species  of  bacteria  differs  greatly :  while  some 
bacteria  are  killed  at  rather  low  temperatures,  others  re- 
quire a  temperature  considerably  above  the  boiling  point. 
To  be  absolutely  certain  that  all  bacteria,  and  above  all 
their  spores,  are  destroyed,  we  should  heat  intensively  for 
every  sterilization.  In  some  cases  this  is  impossible, 
as  many  substrata  cannot  be  heated  very  high  without 
being  changed  in  one  way  or  another.  In  case  of  such 
nutritive  substrata  we  must  therefore  make  use  of  other 
methods  of  procedure.  A  lower  heat  acting  for  a  longer 
time  or  repeatedly  may,  e.g.,  be  applied.  This  last  method 
(intermittent  sterilization)  has  to  be  used,  among  other 
cases,  in  the  sterilization  of  milk  and  its  products. 

Intermittent  Sterilization. — Having  killed  the  vegeta- 
tive forms  of  the  bacteria  through  a  careful  heating,  the 
substratum  is  allowed  to  stand  at  ordinary  temperature  for 
some  time,  so  that  the  spores,  which  of  course  retained  their 
vitality,  may  develop  into  ordinary* bacteria;  and  these  are 
then  in  their  turn  killed  by  a  second  heating.  As  all 
spores  may  not  then  have  reached  the  vegetative  stage, 
or  as  some  new  spores  may  have  been  formed  during  the 
interval,  it  is  safest  to  repeat  the  operation  one  or  more 
times,  according  to  necessities  in  each  case.  To  be  entirely 
safe,  the  milk  is  never  used  until  its  sterility  has  been 


16 


MODERN   DAIEY   PRACTICE. 


ascertained  by  its  being  kept  for  some  time  at  a  tempera- 
ture favorable  to  the  development  of  the  spores  possibly 
still  remaining  in  it. 

Method  of  Sterilization. — Several  different  apparatus 
have  been  constructed  for  sterilization  of  nutritive  media 
through  heat.  The  steam  sterilizing  apparatus  introduced 
into  bacteriology  by  Koch  and  Gaffky  is  generally  used 
in  Northern  laboratories.*  If  this  is  to  be  used  for  the 
sterilization  of  milk,  e.g.,  the  substratum  must  be  exposed 
in  the  apparatus  to  a  temperature  of  212°  F.  (100°  0.)  for 
three  quarters  of  an  hour  each  time  on  three  consecutive 
days.  Other  substrata  require  of  course  a  different  treat- 
ment in  order  that  the  sterilization  may  be  successful.  Milk 
may  also  be  sterilized  in  a  very  short  time  by  being 
heated  under  pressure  at  248°  F.  (120°  0.)  in  a  Chamberland 

*  The  Arnold   Steam-cooker,  an  ordinary  domestic  utensil  in 
America,  is  admirably  adapted  for  purposes  of  sterilization.    (Fig. 
13). 

Water  is  poured  into  the  pan  (or 
reservoir),  whence  it  passes  slowly 
through  three  small  apertures  into  the 
shallow  copper  vessel  (generator)  be- 
neath, becomes  converted  into  steam, 
and  rises  through  the  funnel  in  the 
center  to  the  sterilizing  chamber  above. 
Here  it  accumulates  under  moderate 
pressure  at  a  temperature  of  212°  F. 
The  excess  of  steam  escapes  about  the 
cover,  becomes  imprisoned  under  the 
hood,  and  serves  to  form  a  steam  jacket 
between  the  wall  of  the  sterilizing 
chamber  and  the  hood.  As  the  steam 
FIG.  13.  is  forced  down  from  above  and  meets 

the  air  it  condenses  and  drips  back  into  the  reservoir. — W, 


STERILIZING  CHAMBER 

JL 


BACTERIA   AND   THEIR   RELATION    TO    DAIRYING. 


Steam  Sterilizer.     When  this  method  is  followed,  the  milk 
is,  however,  often  brown  colored 


14 


15  16 

FIGS.  14-17. 


The 


FIG.  14.— Test-tube  closed  with  a  cotton  plug  and  filled  with  gelatine, 
inner  surface  of  the  tube,  the  cotton  plug,  and  the  gelatine  are  sterilized. 

FIG.  15.— Culture  of  a  bacterium  in  a  test-tube.  The  bacterium  has  formed 
a  large  colony  on  the  surface  of  the  gelatine,  and  a  weak  bacterial  growth  is 
shown  in  the  inoculation-needle  track  "  stick.1' 

FIG.  16. — Shows  a  culture  which  peptonizes  (liquefies)  the  gelatine.  A  colony 
is  also  in  this  case  first  formed  on  the  surface  of  the  substratum,  but  as  the 
bacteria  liquefied  this  it  gradually  sank  into  the  liquid  formed.  At  the  stage 
shown  in  the  cut  the  bacteria  appear  as  a  small  precipitate,  c,  at  the  bottom  of 
the  funnel-shaped,  liquefied  gelatine. 

FIG.  1?.— Shows  a  culture  of  bacteria  which  also  liquefied  the  gelatine,  but  to 
a  smaller  extent  than  the  one  last  mentioned.  Before  the  liquefaction,  short 
filaments  grow  out  into  the  solid  gelatine  from  the  "  stick." 


The  sterilization  of  some  substrata  may  be  accomplished 
by  nitration  through  clay,  gypsum,  porcelain,  asbestos 


18  MODERN   DAIRY    PRACTICE. 

paper,  layers  of  sand,  and  so  on,  all  prepared  especially  for 
the  purpose.  These  filters  retain  all  solid  particles  found 
in  the  liquids,  and  consequently  also  the  bacteria.  This 
method  of  sterilization  is  not,  however,  applied  as  often  as 
the  one  previously  given. 

Methods  of  Examination. — The  culture  of  the  bacteria 
takes  place  in  the  laboratory  in  sterilized  glass  vessels  of 
different  shapes.  Ordinary  test-tubes  or  glass  flasks  are 
most  commonly  used;  in  either  case  the  mouth  of  the  ves- 
sel is  closed  by  a  sterilized  cotton  plug.  This  allows  the  air 
to  pass  in  and  out,  but  prevents  bacteria  from  gaining 
access  to  the  vessel  from  the  outside.  Sterilized  gelatine 
plates,  properly  protected  against  infection  from  the  bac- 
teria of  the  air,  are  also  used. 

In  the  bacteriological  examination  of  a  liquid  substance 
this  is  first  examined  through  the  microscope ;  the  different 
kinds  of  bacteria  in  the  substance  are  then  isolated.  This 
is  done  according  to  the  method  invented  by  Koch :  one 
or  two  drops  of  the  liquid  are  introduced  into  a  test-tube 
containing  some  gelatine  which  has  previously  been  lique- 
fied by  careful  heating.  The  sample  is  shaken  carefully 
and  rapidly,  so  that  the  gelatine  cannot  congeal,  and  is 
then  poured  on  a  glass  plate  protected  from  infection  of 
bacteria  and  allowed  to  solidify.  By  the  thorough  shaking 
the  individual  bacteria  in  the  drops  of  the  liquid  are  scat- 
tered in  the  gelatine,  so  that  on  the  congelation  of  the 
latter  they  are  fixed  at  different  places  in  the  same.  If  the 
plate  be  now  kept  under  favorable  conditions  of  tempera- 
ture, light,  and  moisture,  each  one  of  the  single  bacteria 
will  multiply  and  form  colonies  of  varying  sizes,  as  a  rule 
visible  to  the  naked  eye  (see  Fig.  18). 

If  the  sample  does  not  contain  such  an  abundance  of 


BACTEKIA   AND   THEIE  RELATION   TO   DAIRYING.        19 


bacteria  that  the  colonies  go  over  into  one  another,  differ- 
ent nutritive  substrata  may  be  inoculated  with  a  part  of 
the  different  colonies,  and  pure  cultures  are  in  that  way 
obtained  of  the  various  organisms;  provided, however,  that 
the  whole  process  has  been  conducted  with  due  care  and 
dexterity.  When  the  various  species  of  bacteria  found  in 
the  liquid  have  been  isolated  in  this  manner,  they  are 
grown  in  different  substrata  to  study  their  manner  of 
growth  and  effects.  The  determination  of  the  bacterial 


FIG.  18. 

a,  glass  plate;  6,  congealed  gelatine,  in  which  maybe  found  all  kinds  of  colo- 
nies; the  colony  at  c  liquefies  the  gelatine,  the  others  do  not.  The  ramified 
colonies  consist  of  moulds,  the  others  of  bacteria. 

contents  of  water  or  milk  is  as  a  rule  conducted  according 
to  the  method  here  given.  By  this  and  other  bacteriologi- 
cal operations  it  is,  however,  not  enough  to  make  only  a 
single  examination  ;  a  number  of  control  cultures  must 
always  be  made. 

Unfortunately  all  bacteria  cannot  Be  isolated  and 
grown  in  this  easy  manner;  but  the  method  of  procedure 
in  other  cases  cannot  here  be  explained  in  detail,  and  in- 
terested readers  are  referred  to  the  text- books  already 


20  MODERN   DAIRY   PRACTICE. 

mentioned  concerning  this  point,  as  well  as  all  details  in 
bacteriological  technic. 

Before  concluding  this  short  explanation  of  bacteriologi- 
cal methods  of  investigation  I  will  state  that  a  large  num- 
ber of  bacteriological  studies — at  least  in  their  beginning 
— do  not  necessarily  require  for  their  execution  a  complete 
laboratory,  equipped  with  expensive  and  delicate  apparatus. 
A  number  of  simple  pieces  of  apparatus  fit  for  sterilizing 
material  for  bacterial  cultures  at  a  high  temperature,  etc., 
may  be  found  in  almost  any  modern  kitchen.  This  is  of 
great  importance,  since  the  field  of  investigation  cannot 
always  be  near  laboratories.  A  large  portion  of  the  bac- 
teriological studies  upon  which  this  book  is  founded  could 
not,  in  the  nature  of  things,  be  made  in  a  city  laboratory, 
but  were  only  made  possible  because  a  small  so-called 
bacteriological  hand-laboratory  was  amply  sufficient  for 
their  pursuit.  Thanks  to  this  fact  I  have  been  able  to 
conduct  my  investigations  in  the  midst  of  the  industries 
whose  conditions  I  intended  to  study  from  a  bacteriologi- 
cal point  of  view. 

As  an  illustration  of  the  importance  of  bacteria  in  the 
dairy  industry,  I  will  report  an  event  which  strikingly 
shows  how  the  dairy  products  on  a  farm  may  for  a  long 
time  be  entirely  spoiled  on  account  of  infection  from  a 
single  harmful  species  of  bacteria.  On  the  estate  Duelund 
in  Denmark,  belonging  to  Hofjagerrwster  Friis,  who  is 
so  well  known  in  the  Danish  dairy  world,  the  principles 
of  rational  dairying  have  been  followed  since  the  introduc- 
tion of  the  dairy  movement  into  Denmark.  High-grade 
outter  to  which  premiums  were  often  awarded  has  lon£ 
been  made  on  the  estate.  But  about  a  year  ago  it  suddenly 


BACTERIA   AND   THEIR   RELATION   TO    DAIRYING.        21 

became  impossible  to  produce  first-class,  fine-flavored  butter 
in  the  dairy  of  the  estate  in  spite  of  the  fact  that  the  butter- 
making  was  conducted  with  every  possible  care  and  ac- 
cording to  the  same  method  as  before. 

The  milk  was  evidently  not  diseased  when  drawn  from 
the  udder,  but  on  standing  for  a  time  it  invariably  assumed 
a  putrid  smell  and  taste,  which  even  reappeared  in  the 
butter  made  from  the  milk.  The  accident  of  course 
caused  the  loss  of  large  sums  of  money  to  the  owner,  the 
product  of  butter  from  the  estate  being  very  large.  The 
best  dairy  experts  were  consulted,  but  their  directions  were 
of  no  avail.  It  was  then  suspected  that  the  cause  of  the 
evil  was  of  a  bacteriological  nature,  and  Professor  C.  0. 
Jensen,  the  bacteriologist  at  the  Copenhagen  experiment 
station,  was  called  in  to  investigate  the  matter.  After 
having  carefully  studied  the  case  he  ascertained  that  the 
rapid  spoiling  of  the  milk  was  caused  by  a  single  small 
bacterium  which  had  infected  all  the  places  where  the 
milk  was  handled.  He  showed  that  the  small  disastrous 
organism  had  spread  not  only  over  the  barn,  where  it 
was  even  found  on  the  udders  of  the  cows,  but  also  all 
over  the  dairy.  He  isolated  the  bacterium  and  made  it 
the  object  of  lengthy  investigations.  By  introducing 
cultures  of  it  into  sterilized  milk  he  brought  about  the 
same  peculiar  changes  which  characterized  the  diseased 
milk  at  Duelund. 

The  organism  which  caused  so  much  harm  and  loss 
proved,  however,  comparatively  harmless,  thanks  to  its 
poor  power  of  resistance.  It  dies  at  as  low  a  temperature 
as  149°  F.  (65°  C.),  and  besides  may  be  killed  by  means  of 
ordinary  disinfectants.  After  a  disinfection  of  barn  and 


22  MODERN   DAIRY   PRACTICE. 

dairy  it  soon  disappeared  from   Duelund,  and  first-class 
butter  could  again  be  produced  there. 

If  energetic  remedies  for  the  eradication  of  this  bac- 
terium had  not  been  resorted  to  in  time,  and  if  it  had  not 
possessed  such  slight  resisting  properties,  a  milk  epidemic 
might  easily  have  spread  far  around  from  this  "pest- 
house,"  which,  in  spite  of  our  modern  highly-lauded 
rational  dairy  industry,  had  formed  at  one  of  the  most 
carefully-conducted  dairies  in  the  great  dairy  country  of 
Denmark. 


MILK   AS    DRAWN   FROM   THE    UDDER.  25 

In  investigations  concerning  the  original  sterility  of  the 
milk  I  have  followed  a  somewhat  different  plan  from  the 
one  given.  When  the  udder  has  been  cleaned  I  have 
drawn  the  milk  by  means  of  a  sterilized  silver  milking- 
tube,  kept  carefully  protected  from  infection  till  it  is  used. 
Following  this  method  I  have  succeeded  in  obtaining  good 
results,  even  when  the  experiment  was  made  in  the  barn. 
Nearly  all  the  samples  of  milk  remained  unchanged,  al- 
though they  were  kept  for  several  days  in  an  incubator 
(thermostat)  at  a  temperature  of  86°-90°  F.  (30°-32°  C.). 
This  speaks  decidedly  in  favor  of  this  simple  method,  which 
doubtless  is  to  be  preferred  to  the  older  one,  as  the  milk  in 
the  latter  is  far  more  liable  to  infection. 

•  Since  the  milk  when  drawn  from  a  sound  udder  is  abso- 
lutely sterile  and  will  keep, — i.e.,  does  not  contain  any 
micro-organisms, — our  efforts  must  be  directed  toward  pro- 
tecting it  from  infection  in  the  handling  and  further  manu- 
facture in  the  dairy  and  creamery.  We  shall  see  in  the 
next  chapter  that  infection  of  the  milk  by  bacteria*  is 
inevitable,  and  shall  learn  the  best  means  of  protecting 
the  milk  and  its  products  from  the  same. 


^^ j^S^-SSSS^^k. 


24  MODERN  DAIRY   PRACTICE. 

show  the  original  sterility  of  milk  after  the  experience 
gathered  by  the  above-given  scientists.  It  is,  however, 
necessary  strictly  to  observe  certain  precautions.  The 
udder  and  its  environments  must  be  carefully  cleaned  with 
soap  and  water,  treated  with  corrosive  sublimate  solution 
and  washed  with  boiled,  rapidly  cooled  water.  The  milk- 
er's hands  should  be  washed  in  ether  and  alcohol,  then 
rinsed  with  sublimate  solution,  and  carefully  washed  in 
boiled  water.  '  The  milk  is  drawn  into  sterilized  glass 
vessels.  Good  results  are  generally  secured  when  these 
precautions  are  followed,  and  when  the  milking  is  done 
rapidly  and  with  precision,  preferably  at  some  place  away 
from  the  cow-stable  and  other  places  filled  with  micro- 
organisms.* 

*  The  difficulty  which  bacteriologists  have  often  found  in  obtain- 
ing absolutely  sterile  milk,  when  it  has  been  drawn  under  observa- 
tion of  all  possible  precautions,  is  explained  by  the  observation  made 
by  Lehmann,  that  bacteria  found  in  the  drop  of  milk  at  the  opening 
of  the  teat  are  able  to  work  their  way  into  the  milk-cistern,  where 
they  then  multiply  very  rapidly,  favored  both  by  the  high  tempera- 
ture and  the  rich  nutritive  medium.  At  milking  the  bacteria  in  the 
milk-cistern  will  be  largely  washed  out  in  the  first  portions  of  milk 
drawn,  but  all  are  not  removed  until  the  milking  has  progressed  for 
some  time.  Lehmann  (17fe  Versammlung  d.  deut.  Ver.  f.  offent. 
Oesundheiispflege)  thus  found  that  the  first  milk  drawn  (300  cubic 
centimeters,  about  10  oz.)  contained  50,000  to  100,000  bacteria  per 
cubic  centimeter,  while  the  main  quantity  of  the  milk  drawn  con- 
tained 5000  bacteria  per  cc.  on  an  average,  and  the  last  300  cc.  were 
almost  or  entirely  free  from  bacteria.  Schulz  (Arch.  f.  Hyg.t  14,  260) 
in  the  same  way  showed  that  the  first  portion  of  a  milking  contains 
a  large  number  of  bacteria,  while  the  last  portions  of  milk  are  sterile 
when  proper  precautions  have  been  taken.  See  also  Gernhardt, 
Quant.  Spaltpilzunters.  d.  Milch,  Inaug.  Dissert.  Univ.  Jurjew, 
1893.— W. 


PART  I. 

MILK. 


"  Sauberes  Euter,  reine  Hose  und  Hand 
Bringen  zur  Ehre  den  Melkerstand." 

Swiss  Proverb. 


CHAPTER  I. 
MILK  AS  DRAWN  FROM  THE  UDDER 


the  milk  is  drawn  from  the  udder  of  a  healthy 
cow  it  is  germ-free  or  sterile.  Lister,  Meissner,  Duclaux, 
and  other  scientists  have  shown  that  such  milk  will  re- 
main unchanged  for  all  time  without  any  preservatives 
being  added,  if  it  is  only  carefully  protected  from  all  bac- 
terial infection.  The  original  sterility  of  normal  milk  is 
due  to  the  fact  that  the  bacteria  cannot  gain  access  to  the 
milk-glands  from  without  as  long  as  the  udder  is  not 
injured  in  any  way,  and  that  the  udder  can  only  be  in- 
fected by  bacteria  from  within,  from  the  different  internal 
parts  of  the  animal  body,  when  these  parts  themselves  are 
infected  with  bacteria,  i.e.,  are  not  in  their  normal,  healthy 
condition. 

It  is  a  comparatively  easy  bacteriological  experiment  to 

23 


CHAPTEE  II. 

SOURCES  OF  INFECTION  IN  THE  STABLE,  AND  ITS 
PREVENTION. 

ON  its  arrival  at  the  dairy  the  milk  is  always  more  or 
less  infected  with  bacteria,  it  being  impossible  to  pro- 
tect it  entirely  from  infection  in  practical  dairying.  This 
is  apparent  from  the  mere  fact  that  it  is  not  always  possi- 
ble to  keep  the  milk  sterile  even  when  all  precautions  of 
a  scientific  investigation  are  taken.  Lister's  experiments 
concerning  the  original  sterility  of  milk  form  an  interest- 
ing illustration  of  this  matter  ;  although  the  greatest  pre- 
cautions were  taken,  he  obtained  only  a  very  few  milk 
samples  that  would  keep  as  long  as  the  milking  was  done 
in  the  stable.  If  the  milking,  on  the  other  hand,  took  place 
in  the  open  air,  the  experiments  were  nearly  always  suc- 
cessful. It  would  therefore  seem  that  the  air  in  the  cow- 
stable  at  the  time  of  these  experiments  was  so  mixed  with 
bacteria  that  in  spite  of  all  care  it  proved  almost  impossi- 
ble for  him  to  protect  the  milk  from  infection. 

It  is  therefore  evident  that  the  milk  already  in  the 
barn  must  be  highly  infected  with  bacteria  in  its  ordinary 
handling.  It  is,  however,  out  of  the  question  to  introduce 
scientific,  exact  means  of  precautions  in  the  practical  work 
in  the  barn,  in  order  to  prevent  all  infection  of  the  milk, 
as  this  would  make  the  work  too  complicated  and  expen- 
sive, and  some  of  the  precautions  that  would  have  to  be 


SOUKCES  OF  INFECTION  IN   THE   STABLE.  27 

taken  (e.g.),  the  application  of  corrosive  sublimate)  are 
furthermore  dangerous.  Milk  as  found  in  practical  dairy- 
ing has  therefore  lost  its  ability  to  keep  for  an  indefinite 
period  of  time,  and  the  various  bacteria  contained  in  it  are 
trying  to  change  it  in  one  way  or  another.  Fortunately 
we  are  so  situated  that  the  milk  does  not  need  to  be 
entirely  germ-free  (sterile)  for  the  purposes  for  which  it 
generally  is  used,  a  truth  which  practical  experience  has 
long  ago  taught  us.  Experience  has  also  taught  us  that 
the  better  we  succeed  in  preserving  the  original  qualities 
of  the  milk  before  the  process  of  manufacture  begins,  the 
finer  will  the  products  be,  and  above  all  the  better  will 
they  keep.  However  intelligent  and  experienced  a  dairy- 
man may  be,  he  cannot  make  first-class  products  from  milk 
that  has  been  carelessly  handled. 

Since  bacteria  are  found  everywhere,  some  one  may 
object  that  it  cannot  be  worth  the  trouble  to  fight  them. 
A  fight  against  omnipresent  and  even  invisible  enemies 
must  at  any  rate  be  hopeless.  This  reasoning  is  not,  how- 
ever, justified ;  for  we  do  possess  strong  means  of  fighting 
the  bacteria.  In  several  kinds  of  manufacturing  enter- 
prises it  is  already  possible  to  limit  and  govern  the  activ- 
ities of  the  bacteria.  As  an  example  may  be  mentioned 
that  the  standpoint  was  long  ago  reached  by  the  manu- 
facturers of  beer  that  they  no  longer  need  fear  being  dis- 
turbed in  the  normal  progress  of  their  work  through  in- 
vasion of  bacteria,  but  on  the  contrary  may  determine  at 
will  the  kinds  of  yeast  that  are  to  start  the  fermentations 
desired.  Not  until  after  this  was  reached  it  was  possible 
to  make  well-keeping  and  always  uniform  products  in 
this  industry — a  goal  toward  which  dairying,  of  course, 
also  must  aim. 


28  MODERN   DAIRY    PRACTICE. 

While  we  cannot  hope  to  make  a  raw  product  of  abso- 
lute keeping  qualities  in  dairying,  we  must  try  to  make 
it  keep  as  long  as  possible,  i.e.,  we  must  protect  the  milk 
from  being  spoiled  by  bacteria  by  all  means  at  our  dis- 
posal. 

Precautions  against  Infection  of  Bacteria. — The  pre- 
cautions used  against  infection  of  bacteria  are  of  two 
kinds, — (1)  such  as  aim  at  the  protection  of  the  milk  from 
infection  from  without',  and  (2)  such  as  aim  to  check  the 
development  and  multiplication  of  the  micro-organisms 
already  found  in  the  milk.  In  practical  work  these  two 
methods  go  hand  in  hand,  however,  for  which  reason  we 
shall  not  here  attempt  a  strict  separation. 

Infection  during  Milking, — The  milk  is  exposed  to 
infection  from  the  moment  it  is  drawn  from  the  udder. 
Being  pressed  out  of  the  teats  in  a  fine  spray,  it  comes  in 
contact  with  the  air  on  a  very  large  surface  ;  the  air  in 
the  cow-stable,  and  especially  under  the  udder  region  of 
the  cow,  is  nearly  always  filled  with  such  bacteria  as  are 
the  feudal  enemies,  so  to  speak,  of  the  milk.  If  the 
milking  is  done  in  the  open  air,  e.g.,  in  the  pasture,  the 
danger  of  infection  is  of  course  less.  It  can  easily  be 
shown  by  a  bacteriological  examination,  however,  that 
there  is  a  danger  also  in  this  case.  By  the  shaking  to 
which  the  udder  and  the  parts  of  the  skin  next  to  the 
same  are  subjected  in  milking,  bacteria  are  always  loosened 
in  large  numbers  and  infect  the  air  and  the  milk.  This 
is  plainly  shown  by  the  following  simple  experiment : 

Of  two  sterilized  culture-plates  with  nutritive  gelatine, 
which  had  been  freed  from  all  bacterial  life  by  steriliza- 
tion, one  was  placed  five  to  six  feet  away  from  the  milker 
and  the  cow,  and  the  other  directly  under  the  udder, 


SOURCES  OF  INFECTION  IN  THE  STABLE.       29 

next  to  the  upper  rim  of  the  milk-pail.  When  the  milk- 
ing began  both  plates  were  uncovered  at  the  same  time, 
so  that  the  bacteria  gained  free  access  to  the  gelatine. 
After  a  moment  both  specimens  were  again  covered  at  the 
same  time.  The  bacteria  were  then  allowed  to  develop  in 
the  gelatine  for  twenty-four  hours  or  more,  when  they 
formed  colonies;  and  it  could  be  observed  with  the  naked 
eye  that  a  many  times  larger  number  of  bacteria  fell  into 
the  dish  placed  under  the  belly  of  the  cow  than  into  the 
one  placed  farther  away. 

If  this  experiment  is  made  in  a  stable  filled  with  cows, 
the  infection  arising  from  the  body  of  the  cows  will  be 
shown  still  more  plainly,  as  the  cows  are  then  far  more  in- 
fected by  bacteria  than  in  the  free  air.  It  is  important  in 
experiments  of  this  kind  in  the  stable  to  place  the  dishes 
at  the  same  height  from  the  floor,  as  there  is  a  considerable 
difference  between  the  bacterial  contents  of  the  upper  and 
lower  layers  of  the  atmosphere  in  a  stable.  If  the  direc- 
tions given  are  followed  it  will  be  found,  as  in  my  experi- 
ments, that  although  a  goodly  number  of  bacteria  will  fall 
into  both  plates,  the  sample  placed  under  the  udder  will 
contain  a  much  larger  number  of  bacteria  than  the  plate 
placed  a  little  away  from  the  cow. 

These  experiments  show  the  truth  of  the  fact  known 
long  ago,  but  often  overlooked,  that  it  is  very  important  to 
keep  the  skin  of  the  cows  as  clean  as  possible. 

Importance  of  Proper  Bedding. — The  first  point  to  ob- 
serve in  this  regard  is  to  provide  the  cows  with  bedding  of 
dry,  clean  straw.  The  cows  are  often  left  to  lie  in  manure 
and  other  filth — a  condition  which  nullifies  all  precautions 
taken  later  on.  Remnants  of  manure,  etc.,  may  be  seen  by 
a  microscope  in  the  milk  from  cows  taken  fairly  good  care 


30  MODERN   DAIRY   PRACTICE. 

of.*  What  an  abundance  of  such  filth  and  of  the  bacteria 
always  prolific  in  such  environments  must  there  not  be 
found  in  the  milk  from  stables  where  uncleanliness  of  this 
kind  reigns  supreme. 

Relation  of  Grain-raising  to  Cleanliness  in  the  Stable. — 
In  days  gone  by,  when  the  production  of  grain  was  the 
most  important  system  of  agriculture  practised,  there  was 
an  abundant  supply  of  straw  on  the  farms,  and  plenty 
could  be  used  as  litter  for  the  cows.  The  fact  that  the 
feeding  was  not  as  intense  as  now  also  made  it  easier  to 
keep  the  cows  clean.  The  feed  consisted  mainly  of  hay  and 
straw,  and  produced  a  dry,  only  slightly  offensive  manure. 
Now,  on  the  other  hand,  there  is  only  a  limited  supply  of 
straw  on  the  farms,  and  the  high  feeding  practised  makes 
it  considerably  harder  to  keep  the  cows  clean,  as  it  makes 
the  dung  watery  and  of  a  very  offensive  smell.  In  our 
days,  when  the  demands  for  cleanliness  in  the  stable  are 
becoming  more  and  more  strict,  the  farmer  has  there- 
fore greater  difficulties  to  overcome  in  trying  to  fulfil 
these  demands,  at  the  same  time  as  he  often  has  lost  the 
best  remedy  previously  at  his  disposal  to  reach  this  end. 
The  explanation  of  the  above-mentioned  fact  that  a  large 
number  of  dung  and  food  particles  and  other  impurities 
may  be  found  by  a  microscope  even  in  strained  milk  from 
comparatively  well-kept  cow-stables,  doubtless  lies  here. 
The  danger  to  the  keeping  qualities  of  the  milk  from  this 
source  arises  from  the  fact  that  these  particles  are  carriers 
of  a  considerable  number  of  bacteria.  I  have  repeatedly 
observed  that  a  large  number  of  spore-bearing  bacteria 

*  See  Gripenberg  and  Grotenfelt :  Illustrations  of  Cows'  Milk, 
Cream,  etc.  (Afbildningar  af  komjOlk,  gradde  m.  m.),  Helsingfors, 
1889,  p.  11,  Fig.  Vila. 


SOURCES  OF   INFECTION   IN  THE   STABLE.  31 

and  free  spores  were  found  on  the  contaminating  particles 
in  milk  fresh  from  the  cow,  while  such  ones  did  not  appear 
to  any  appreciable  extent  in  the  milk  itself.  After  some 
time  the  impurities  showed  a  far  smaller  number  of  bac- 
teria than  before,  while  the  milk  itself  teemed  with  them; 
the  milk  may  therefore  be  infected  even  from  the  impuri- 
ties introduced  in  the  same. 

At  the  same  time  as  I  made  these  observations  I  found 
micro-organisms  and  spores  outside  of  the  milk  of  exactly 
the  same  kinds  as  those  found  on  the  impurities  of  the 
milk,  viz.,  in  the  manure  remnants  which  had  had  a  chance 
to  remain  for  a  time  in  the  warm  and  moist  atmosphere  of 
the  stable,  and  thereby  became  the  seat  of  a  luxuriant  bac- 
terial growth,  and  also  in  the  dirt  on  the  skin  of  the  cows, 
where  the  bacteria  may  develop  rapidly,  greatly  benefited 
by  the  animal  heat  and  moisture. 

Impurities  in  the  Milk. — As  the  impurities  which  get 
into  the  milk  even  during  the  milking  itself  play  such  an 
important  part  in  the  infection  of  bacteria,  it  is  important 
to  learn  their  origin.  The  microscopic  examination  gives 
a  good  indication  of  their  origin.  I  have  found  the  fol- 
lowing kinds  of  impurities  in  unstrained  milk  fresh  from 
the  cow : 

1.  Manure-particles  (numerous). 

2.  Fodder-particles  (which  have  not  passed  the  aliment- 
ary canal  of  the  animals). 

3.  Molds  and  other  fungi. 

4.  Cow-hair  (numerous). 

5.  Particles  of  the  skin. 

6.  Human  hair. 

7.  Parts  of  insects.  ^^x^/$>/ 

8.  Down  from  birds. 


32  MODERN   DAIRY   PRACTICE. 

9.  Small  wooden  pieces,  shavings,  and  pieces   of  fir- 
leaves. 

10.  Woollen  threads. 

11.  Linen  threads. 

12.  Soil-particles  (rather  frequent)  and  moss -particles. 

13.  Fine  threads  (most  likely  cobwebs),  etc. 

In  these  investigations  I  also  found  several  impurities 
in  the  milk  whose  presence  I  was  unable  to  explain,  as,  e.g., 
cheesy  lumps,  slimy  substances  with  a  firmer  nucleus,  shin- 
ing, fat-like  bodies,  fine  floss  and  grains,  and  similar 
matters.  As  regards  the  liquid  impurities  appearing  in 
the  milk,  it  need  hardly  be  mentioned  that  they  cannot  be 
detected  by  microscopic  examination.* 

*  The  quantities  of  solid  impurities  in  milk  have  been  deter- 
mined by  Renk  (MuncTiner  Ned.  Wochenschr.,  1891,  Nos.  6  and  7;  Gen- 
tralbl.f.  Bact.,  10,  193),  Schulz  (Arch.  f.  Hyg.,  14,  260),  Vogel  (Ber. 
Qes.  Verb.  v.  Nurnberg,  1891,  78),  Uhl  (Zeitschr.f.  Hygiene,  12,  475), 
and  Ostermayer  (Inaug.  Dissert.  Univ.  Halle,  1891).  Renk  examined 
ninety  samples  of  market  milk  and  found  the  following  average 
quantities  of  impurities  (mainly  dung  particles)  in  the  milk  of  the 
cities  given.  The  fresh  substance  is  calculated  on  basis  of  an  80-per- 
cent water- content  of  the  impurities : 

Leipsic.  Munich.    Berlin.  Halle  a.  S. 

Dry  substance,  milligrams  per  liter     3.8         9.0       10.3       14.9 
Fresh  substance,          "          "      "     19.0       45.0       51.3       74.6 

The  maximum  quantities  of  impurities  were  found  in  case  of  a 
sample  of  Halle  milk,  containing  372.5  milligrams  of  fresh  impuri- 
ties per  liter  (nearly  6  grains  per  quart). 

Schulz  determined  the  quantities  of  microscopic  impurities  in 
Wurzburg  milk,  as  sold  in  the  city  (I),  as  bought  in  the  country  (II), 
and  as  milked  into  a  glass  jar  (III) : 

i.     n.     ra. 

Dry  substance,  milligrams  per  liter 3.0    1.7      2.3 

Fresh  substance,        "  "      "    15.1    8.6    11.5 

The  milk  in  case  of  I  and  II  was  strained  through  a  fine  gauze 


SOURCES   OF   INFECTION   IN  THE   STABLE.  33 

It  is  natural  to  suppose  that  a  good  many  of  the  con- 
taminating particles  mentioned  above  came  into  the  milk 
through  the  litter  used  ;  this  may  thus  both  indirectly  and 
directly  contribute  to  the  infection  of  the  milk.  Proper 
litter  must  not  only  form  a  good  bed  and  quickly  absorb 
the  liquids,  but  must  also  as  far  as  possible  be  free  from 
dust  and  all  kinds  of  soil  particles,  fungi,  etc.  We  often 
find  litter  in  our  stables,  however,  which  does  not  come 
up  to  these  requirements.  I  may  mention  as  an  example 
that  in  several  places  where  the  generally  excellent  peat 
dirt  has  been  introduced  they  have  neglected  to  remove  its 
dust  particles  as  directed.  As  a  result  I  have  found  large 
quantities  of  humus  and  sphagnum  particles  in  the  milk 
from  farms  where  this  practice  was  followed.  I  have  also 
found  fungi  of  all  kinds  in  the  milk  from  a  stable  where 
the  fodder  and  straw  litter  were  impure  and  moldy  owing 
to  bad  weather  during  the  harvest.  The  milk  from  a  farm 
where  they  used  pine  leaves  as  a  litter  was  found  very 
impure,  especially  from  manure  particles,  an  observation 
which  would  indicate  that  this  material,  which  also  for 
other  reasons  is  undesirable,  ought  not  to  be  used  as  litter 
on  dairy-farms.  The  sample  of  milk  mentioned  last  also 
contained  large  masses  of  molds. 

The  Flooring  of  the  Stable. — An  improper  floor  may 
also  be  the  cause  of  infection  of  the  milk,  as  may  appear 
from  the  fact  that  the  sample  of  milk  which  proved  most 
filled  with  soil  particles  in  my  investigations  came  from  a 
farm  where  the  floor  in  the  stable  consisted  of  bowlders 

strainer.  Vogel  found  12.9  milligrams  dry  impurities  per  liter  of 
JJiirnberg  milk,  and  Uhl  found  19.7  milligrams  per  liter  of  Gies- 
een  milk  (average  results). — "W» 


34  MODERN   DAIEY    PRACTICE. 

partly  covered  with  clay.  At  the  front  feet  of  the  cows 
this  was  usually  dry  as  powder  and  dustlike,  while  in  the 
back  of  the  stall  it  was  solid  and  moist.  At  milking  the 
cows  often  stamp  their  front  feet,  and  it  is  highly  probable 
that  the  milk  in  this  way  became  filled  with  soil  particles. 

Cow  Stalls. — A  too  long  stall  may  indirectly  be  the 
cause  of  infection  of  the  milk.  The  hindquarters  of  the 
cow  will,  under  this  condition,  be  soiled  by  the  manure 
when  she  lies  down.  This  is  especially  the  case  with  the 
tail,  to  which  particular  attention  must  always  be  paid  in 
cleaning  the  cows.  The  cow  will  often  swing  her  tail  dur- 
ing the  milking,  and  if  it  is  soiled,  filth  will  of  course  be 
spread  to  all  sides.  I  have  found  that  the  milk  may  in 
this  manner  be  mixed  with  dirt  of  the  most  offensive  kind. 
At  a  farm  where  the  stalls  were  too  short,  and  where  there 
was  no  litter  in  the  liquid-manure  gutter,  the  cows7  tails 
were  always  wet  and  dirty;  when  the  cows  lay  down  their 
tails  lay  in  the  gutters,  which  did  not  thoroughly  drain 
off  the  liquid  manure.  Although  the  gutters  were  new 
holes  and  recesses  had  already  formed  in  them,  in  which 
the  urine  and  liquid  manure  remained  and  formed  pools. 
By  applying  wooden  shavings  in  the  gutters  the  difficul- 
ties mentioned  were  later  on  avoided.  The  cows  could 
then  be  kept  clean,  and  the  milk  became  as  a  consequence 
cleaner,  and  kept  better  than  was  previously  the  case.  I 
have  met  with  liquid-manure  gutters  of  even  worse  defects 
than  the  ones  described  in  a  large  number  of  stables  in  our 
country. 

On  another  farm,  considered  a  dairy-farm  par  excellence, 
all  the  stalls  were  too  short  for  the  large  fine  cows, « so 
that  the  hind  quarters  and  the  tails  always  lay  in  the  low 


SOURCES   OF   INFECTION    IN   THE   STABLE.  35 

gutter;  the  udders  of  a  number  of  the  cows  were  also  dirty. 
What  made  the  matter  still  worse  was  the  fact  that  the 
stalls  were  lower  than  the  barn-yard  outside,  where  the 
manure-heap  was  placed.  As  a  consequence  the  liquid- 
manure  gutter  was  always  full  of  urine.  Only  a  couple  of 
months  after  the  herd  came  in  from  pasture,  these  sad 
conditions  had  conquered  all  the  efforts  of  the  farm-hands 
to  keep  the  animals  clean  to  such  an  extent  that  the  hind 
quarters  and  parts  of  the  udders  were  covered  with  a  thick 
manure-crust,  and  the  tail  formed  one  solid,  sticky  mass. 
How  impure  the  milk  from  this  farm  must  have  been  may 
easily  be  imagined.  I  cannot  give  any  exact  data  to  what 
extent  it  was  mixed  with  impurities,  as  I  was  not  able  to 
examine  it  closely ;  but,  judging  from  the  large  quantity  of 
slime  gathered  in  the  separator  bowl  when  the  milk  was 
separated,  it  was  as  one  would  expect  from  its  antecedents. 
Conditions  similar  to  those  given  above,  although  not 
carried  to  such  an  extreme,  may  be  found  on  other  of  our 
"  dairy  farms  " — i.e.,  on  farms  where  they  try,  at  least  in  the 
stable,  to  maintain  a  high  standard  of  cleanliness.  What 
can  then  be  expected  of  the  cow-stables  in  the  places  where 
they  do  not  try  at  all  to  follow  the  fundamental  principle 
of  modern  dairying — strict  cleanliness  ?  The  poor  ani- 
mals are  kept  in  such  places  in  undisturbed  peace  through- 
out the  winter,  uncarded  and  uncleaned;  they  are  further- 
more often  confined  in  darkness  for  several  months,  as  the 
very  small  windows  are  often  wholly  snowed  or  frozen 
over.  Cow-stables  where  such  bad  conditions  exist  are 
still  found  in  many  places;  and  still  people  wonder  that 
the  milk  coming  from  these  primitive  stables  is  of  poor 
quality,  and  that  the  products  made  from  it  do  not  keep 
well. 


36  MODERN   DAIRY   PRACTICE. 

We  saw  in  the  preceding  what  a  microscopic  examina- 
tion of  such  milk  would  reveal.  It  is  perhaps  not  possible 
to  express  through  exact  figures  how  such  milk  compares 
with  milk  from  well-conducted  farms  as  regards  the  quan- 
tity of  impurities  which  they  contain,  but  by  a  very  simple 
examination  everybody  possessing  a  microscope — a  very 
cheap  one  will  do — may  satisfy  himself  that  the  difference 
is  very  large.*  In  the  milk  produced  on  farms  where 
strict  cleanliness  is  observed,  the  contaminating  particles 
are  not  only  far  less  numerous,  but  also  of  another 
kind  than  in  the  milk  from  poorly-kept  stables.  It  may 
of  course  happen  that  considerable  quantities  of  fodder 
particles  may  be  found  in  the  former  kind  of  milk;  but 
with  a  few  exceptions  these  have  not  passed  through  the 
animals,  and  are  therefore  not  so  well  suited  to  being  hot- 
beds for  the  development  of  bacteria  as  the  numerous 
manure  particles  in  the  latter  kind  of  milk.  The  milk 
from  a  poorly-kept  farm  also  contains  a  much  larger  num- 
ber of  spores  of  bacteria  than  milk  from  a  well-kept  farm. 
In- extreme  cases  it  is  possible  to  tell  these  two  kinds  of 
milk  from  one  another  without  a  microscopic  examination, 
since  the  more  viscous  and  slimy  milk  from  poorly-kept 
farms  will  pass  through  a  fine  strainer  much  more  slowly 
than  milk  produced  on  carefully-conducted  farms. 

Importance  of  Keeping  Cows  Clean. — The  importance 
of  carefully  carding,  brushing,  and  cleaning  the  cows  is 

*  Renk  (Munchner  Med.  Wochenschr.  1891,  Nos.  6  and  7)  found 
the  following  quantities  of  solid  impurities  in  the  nrilk  from  different 
farms  around  Halle,— viz.,  2.9,  7.3,  7.5,  9.4,  17.9,  37.2  milligrams  per 
liter  (quart)  of  milk.  He  says  that  the  high  content  of  impurities  in 
Halle  milk  is  due  to  "  insufficient  inspection,  the  feeding  of  roots, 
and  the  use  of  peat  for  bedding." — W. 


SOURCES  OF  INFECTION  IN  THE  STABLE.       37 

apparent  from  the  investigations  reported.  If  the  skin  is 
smooth  and  shining,  even  a  little  uncleanliness  is  easily 
discovered,  besides  which  a  cow  well  taken  care  of  does  not 
lose  her  hairs  so  often,  and  they  are  not  so  loose  that  they 
easily  rub  off  during  the  milking.*  In  cleaning  a  cow  we 
ought  not  to  have  our  attention  mainly  directed  to  the 
upper  parts  of  her  body,  as  is  usually  the  case;  but  her 
lower  parts  must  first  of  all  be  kept  properly  cleaned,  since 
it  is  from  these  parts  that  hair  and  other  impurities  prefer- 
ably fall  into  the  milk. 

If  the  more  tender  lower  parts  of  the  cows  cannot  be 
carded,  they  must  be  brushed  and  washed  so  much  the 
more  frequently.  The  tenderness  of  these  parts  will,  how- 
ever, disappear  as  the  cow  becomes  accustomed  to  their  be- 
ing cleaned.  If  these  parts  of  the  bodies  of  the  animals  are 
badly  soiled,  they  can  only  be  cleaned  again  with  a  good 
deal  of  trouble,  through  repeated  moistening  and  washing 
with  soap  and  water.  If  it  becomes  necessary  to  wash  the 
udder  it  should  be  done  rapidly,  and  the  udder  must  then 
be  well  dried  with  a  dry  rag,  as  it  will  otherwise  easily  take 
cold  if  exposed  to  draught,  etc. 

In  summer-time  the  cleaning  of  the  cows  is  often  neg- 

*  Aside  from  the  purely  bacteriological  aspects  of  the  question 
there  is  a  no  less  important  advantage  in  carding  and  brushing  cows 
in  the  resulting  increased  feeling  of  well-being  of  the  cows,  which 
may  find  expression  in  a  larger  production  of  milk  and  fat.  Dietzch 
("  Die  Kuhrnilch,"  p.  21)  states  that  "it  has  been  found  by  experi- 
ments that  cows  kept  in  a  clean  condition  gave,  on  an  average,  1  liter 
(quart)  of  milk  daily  more  than  the  same  cows  in  a  dirty  condition. 
Backhaus  (Journal  f.  Landwirtschaft,  41,  333-42)  also  found  an  ap- 
preciable increase  in  the  milk-yield  of  cows  on  two  different  experi- 
ments. Cf.  the  German  adage,  Out  geputet  ist  halb  gefuttert  ("  Well 
cleaned  is  half  fed  ").—  W. 


38  MODERN    DAIRY    PRACTICE. 

lected  in  the  belief  that  they  keep  themselves  clean  in  the 
pasture.  It  is,  however,  easy  to  satisfy  one's  self  that  it  is 
both  useful  and  necessary  even  then  to  brush  them  occa- 
sionally. The  udders  and  bellies  of  the  cows  are  easily 
soiled  by  dust,  dirt,  and  the  like,  which  is  fastened  loosely 
in  the  skin,  and  by  the  milking  shaken  down  into  the 
milk.  In  this  connection  I  want  to  tell  our  farmers 
that  they  ought  not  to  think  too  much  of  the  trouble  of 
driving  the  cows  from  the  pasture  to  some  neighboring 
lake  or  stream  to  bathe,  where  any  such  is  at  hand.  The 
cattle  gain  not  a  little  in  general  health  thereby,  and  their 
bodfies,  and  above  all  the  lower  parts,  in  that  way  get  a 
thorough  washing.  In  our  land,  rich  in  lakes,  such  summer 
baths  might  be  given  the  cattle  much  oftener  than  is  now 
usually  the  case. 

Even  if  all  due  care  is  taken  in  regard  to  the  cleaning 
of  the  cows  it  is  always  necessary  just  before  the  milking 
to  give  the  udder  and  its  surroundings  a  further  brushing, 
to  remove  all  dust  and  filth,  which  otherwise  would  fall 
into  the  milk.  It  will  not  do  to  excuse  the  neglect  of  this 
act  of  cleanliness  by  saying  that  the  milk  will  be  strained 
and  the  dirt  thus  be  removed  from  it  anyway.  First,  a  large 
portion  of  the  impurities  is  so  finely  divided  that  it  is  not 
arrested  by  the  strainer;  and,  secondly,  the  short  time  elaps- 
ing between  the  milking  and  straining  is  often  sufficiently 
long  to  allow  large  numbers  of  bacteria  to  be  washed  from 
the  impurities  and  to  begin  multiplying  in  the  milk.  The 
udders  must  not  remain  wet,  as  in  such  cases  bacteria  and 
dirt  would  accompany  drops  of  water  which  may  fall  down, 
and  would  infect  the  milk.  The  parts  mentioned  ought, 
on  the  other  hand,  to  retain  some  moisture,  as  dust  and 


SOURCES   OF   INFECTION   IN    THE   STABLE.  39 

dirt  particles  possibly  remaining  will  then  not  so  easily  be 
shaken  down. 

Cleanliness  in  the  Milker. — The  milker  must  be  aware 
of  the  fact  that  he  may  spoil  the  milk  by  untidiness  and 
carelessness.  He  himself  must  be  cleanly,  should  wear 
neat  clothes  and  a  clean  apron. 

In  what  contrast  to  this,  as  it  would  seem,  simple  rule 
is  not  the  manner  in  which  our  milkers  usually  appear  in 
the  cow-stable.  It  seems  to  have  become  almost  a  tradi- 
tion that  the  farm-hands  may  be  dressed  carelessly  and 
slovenly  while  doing  their  work,  and  in  most  places  the 
clothes  are  the  same  for  all  kinds  of  work  done  in  the  barn. 
They  often  go  to  the  milking  in  the  same  costume  and 
with  the  same  unclean  hands  as  to  the  cleaning  of  the 
stable.  And  we  often  see  that  the  milkers  as  they  get 
out  of  bed  in  the  morning  go  unwashed  and  unkempt  to 
the  milking,  dressed  in  the  most  ragged  and  dirty  articles 
of  clothes  in  their  possession.  It  is  certainly  strange  that 
such  carelessness  is  allowed  to  pass  unnoticed  on  most 
farms. 

In  this  connection  attention  may  properly  be  called  to 
the  unfortunate  condition  that  clothes  especially  used  for 
the  work  in  the  barn  in  many  places  are  kept  day  after  day 
in  the  cow-stable ;  they  are  never  aired  or  washed, — a  fact 
which  is  but  too  plain  from  their  offensive  smell.  It  is 
almost  impossible  to  calculate  how  much  mischief  such 
dirty  articles  of  clothing  may  cause  in  regard  to  both  the 
health  of  the  milkers  and  the  taste  and  keeping  quality  of 
the  milk.  Such  "small  matters"  often  give  a  clue  to 
diseases  of  the  milk,  of  which  many  complain  without 
understanding  their  cause.  One  condition  of  getting  rid 
of  these  diseases  is  therefore  that  the  clothes  of  the  milkers 


40  MODERN   DAIRY   PRACTICE. 

be  made  of  wash-goods,  and  that  they  be  often  aired  and 
washed.  The  milking  is  certainly  so  important  that  due 
attention  ought  to  be  paid  to  all  circumstances  in  connec- 
tion with  it. 

The  observation  of  constant  and  strict  cleanliness  and 
the  wearing  of  proper  clothing  on  the  part  of  the  milkers 
would  furthermore  help  to  raise  their  moral  and  social 
standing.  Here  is  not,  however,  the  place  to  dwell  on  this 
side  of  the  question,  and  I  shall  only  call  attention  to  the 
motto  at  the  beginning  of  this  part,  which  expresses  what 
the  Swiss  think  about  this  matter. 

Wash-water  for  Milkers7  Hands.— The  milker  must 
be  particularly  careful  to  clean  his  hands  previously  to 
the  milking.  They  may  easily  come  in  contact  with  the 
milk  during  the  milking,  and  thus  cause  a  direct  in- 
fection. After  having  milked  a  cow  he  ought  to  care- 
fully rinse  his  hands  in  clean  water.*  I  have  found  a 
bad  practice  in  this  line  in  many  places — viz.,  that  the 
water  used  for  washing  the  hands  is  not  changed;  no 

*  This  may  seem  an  unnecessary  precaution  to  many,  but  at 
least  in  case  of  sick  or  diseased  cows  in  a  herd  the  direction  given 
should  be  strictly  followed.  Nocard  and  Mollereau  (see  Bang,  Re- 
port 14,  Copenhagen  experiment  station,  1885,  p.  15)  have  called 
attention  to  the  fact  that  the  milker  may  often  be  the  cause  of  carry- 
ing contagion  from  one  cow  to  another.  They  give  the  following 
experience:  "  A  cow  was  sent  to  Paris  by  rail  and  as  she  came 
from  the  car  she  was  milked  by  a  milker  from  a  neighboring  stable, 
where  inflammation  of  the  udder  for  a  long  time  had  appeared. 
Hardly  six  weeks  after  she  had  been  placed  in  a  previously  healthy 
herd  it  was  noticed  that  her  udder  was  caked;  the  milk  became 
unsalable,  and  the  disease  soon  spread  to  the  majority  of  the  other 
cows  in  the  stable.  It  was  ascertained  that  the  disease  did  not  ap- 
pear in  the  stable  from  where  the  cow  came."— W. 


SOURCES  OF   INFECTION   IN  THE   STABLE.  41 

matter  how  many  the  milkers  and  cows  are,  the  same,  and 
often  scant  supply  of  water  has  to  do  service  for  all  through- 
out the  milking.  It  is  natural  that  bacteria  in  this  way 
will  accumulate  in  the  wa-ter,  and  that  the  washing  will  do 
more  harm  than  good.  The  practice  which  some  persons 
have  of  dipping  their  fingers  into  the  milk  during  the 
milking,  in  order  to  give  them  the  desired  degree  of  moist- 
ure, is  nothing  short  of  horrid. 

Milking  with  Wet  Hands. — The  milking  ought  in  no 
case  to  be  done  with  wet  hands — a  custom  so  common  that 
we  even  sometimes  hear  it  asserted  that  it  is  impossible  to 
milk  with  dry  hands.  This  is,  however,  not  only  possible, 
but  far  more,  an  absolute  necessity.  Milking  with  wet  hands 
cannot  be  a  clean  operation,  a  Danish  author  says,  and 
correctly ;  for  even  if  the  teats  are  wiped  dry  and  cleaned 
in  the  most  careful  manner  they  are  not  so  clean  but  that 
the  hands  of  the  milker,  if  wet,  may  be  soiled  by  touching 
them. 

Manner  of  Milking. — The  milking  is  with  us  usually 
done  in  the  way  that  two  fingers,  or  at  best  the  whole  hand, 
is  made  to  press  along  the  teats,  and  the  milk  is  thus 
driven  out  of  them.  This  method  is,  however,  to  be  re- 
jected. The  strong  pulling  on  the  teats  is  not  agreeable 
to  the  cows,  and  may  even  give  rise  to  cracking  and  dis- 
eases of  the  udder.  The  milk  is  not  formed  in  the  teats, 
and  the  elaboration  of  the  milk  is  not  therefore  forwarded 
by  stretching  them.  Only  by  a  deliberate  and  quiet  press- 
ure of  the  milk  out  of  the  teats  and  an  irritation  of  the 
lower  part  of  the  udder  can  a  complete  clean-milking  be 
obtained,  and  at  the  same  time  the  secretion  of  milk  will  be 
promoted.  The  method  of  milking  common  with  us  ought 
to  be  rejected  for  the  further  reason  that  it  contributes 


42  MODERK  DAIRY  PRACTICE. 

greatly  to  the  infection  of  the  milk.  As  the  fingers  rub 
down  along  the  teats  they  loosen  and  pull  into  the  milk 
all  the  dirt  which  was  not  removed  by  the  washing  of  the 
udder.  The  hands  of  the  milker  furthermore  often  come 
in  contact  with  the  milk  by  the  strong  pulling  of  the  teats, 
and  dirt  adhering  to  the  hand  may  thus  be  washed  into 
the  milk-pail.  If  dairy  products  of  the  highest  quality  are 
wanted,  this  method  of  milking  must  therefore  be  done 
away  with,  and  the  milking  performed  in  a  way  similar  to 
the  following  given  by  a  Danish  writer : 

"  Take  hold  of  the  udder  with  the  whole  hand,  so  that 
the  small  finger  will  be  held  just  so  low  that  the  stream  of 
milk  coming  from  the  teat  cannot  wet  the  finger  or  the 
lower  part  of  the  hand.  The  hand  is  then  lifted,  opening 
it  at  the  same  time  so  that  it  takes  hold  of  the  teat  very 
loosely,  with  a  quick  but  soft  pressure,  and  is  then  lowered 
so  far  that  the  teat  is  stretched  just  to  its  natural  length. 
At  the  same  time  as  the  hand  is  brought  downward,  begin 
to  press  the  teat  from  above  downward,  and  end  with 
squeezing  the  milk  out  with  an  increasing  pressure  of  the 
whole  hand.  This  pressure,  with  a  soft  push  into  the  udder, 
is  a  splendid  means  of  emptying  the  udder.  The  move- 
ments must  not  be  violent,  however,  but  soft  and  at  the 
same  time  as  energetic  as  possible.  Finally,  when  only 
a  little  milk  remains  in  the  udder,  the  milking  is  continued 
in  the  same  manner,  only  with  the  difference  that  the  hand 
is  entirely  loosened  from  the  teat  every  time  it  is  carried  up 
toward  the  udder,  and  the  lower  part  of  the  udder  is  held 
by  the  thumb  on  one  side  and  the  other  fingers  on  the 
other  side;  the  udder  is  then  given  a  couple  of  soft  pushes, 
and  the  milk  pressed  out  in  the  manner  given." 

The  picture  in  the  text,  taken  from  Ugeskrift  for  Land- 


SOURCES   OF   IKFECTION 


THE   STABLE. 


43 


mdnd  for  1890,  from  which  the  above  quotation  is  taken, 
shows  the  proper  position  of  the  hand  in  milking.  The 
milk  ought  to  be  pressed  out  of  the  udder  in  regular  unin- 
terrupted streams,  so  that  it  may  be  exposed  to  infection  for 
as  short  a  time  as  possible,  this  being  especially  threaten- 


FIG.  19. — PROPER  POSITION  OF  HANDS  IN  MILKING. 

ing  when  a  fluid  comes  in  contact  with  the  air  on  a  large 
surface. 

The  milker  must  always  be  quiet  and  deliberate  in  his 
movements  in  the  stable,  and  on  approaching  a  cow  ought 
to  speak  gently  to  her.  If  the  cow  is  disturbed  by  knocks 
and  pushes,  as  is  often  the  case,  she  becomes  impatient  and 
nervous  during  the  milking.  She  moves  from  place  to  place, 


44  MODERN   DAIRY   PRACTICE. 

shakes  herself,  and  lifts  her  feet,  movements  which  set 
legions  of  infectious  germs  in  motion  in  the  immediate 
neighborhood  of  the  milk.  If  the  cow  is  restless  during 
the  milking  the  milk-pail  may  also  easily  be  kicked  over, 
and  dirt  and  filthiness  of  all  kinds  may  be  thrown  into  the 
milk.  Quiet  and  deliberate  manners  in  the  milker  are 
therefore  an  advantage  even  in  regard  to  the  preservation 
of  the  original  qualities  of  the  milk  to  the  largest  extent 
possible. 

Usually  the  teats  are  moist  after  the  milking  is  over 
on  account  of  the  irritation  of  the  skin,  splash,  etc.  If 
this  moisture  remains,  something  like  a  membrane  is 
formed  around  the  teat;  colonies  of  bacteria  quickly  de- 
velop in  this  moist  and  warm  membranous  covering.  The 
teats  ought,  therefore,  to  be  wiped  off  after  the  milking  is 
finished. 

Abnormal  Milk. — The  milker  should  closely  observe  the 
appearance  of  the  milk  during  the  milking,  to  see  whether 
it  is  normal  when  drawn.  If  it  has  an  unusual  appearance 
it  should  by  no  means  be  mixed  with  the  rest  of  the  milk. 
We  sometimes  find  that  the  milk  from  sick  cows  is  bloody, 
filled  with  cheesy  particles,  or  otherwise  abnormally  changed. 
When  milkers  meet  with  such  milk  they  often  quietly  mix 
it  in  with  the  rest  of  the  milk  if  its  abnormal  qualities  are 
not  very  strongly  marked.  In  this  way  large  quantities  of 
milk  may  be  infected,  and  if  the  temperature  is  favorable 
for  bacterial  development,  accidents  may  take  place.  If 
the  milk,  on  the  other  hand,  looks  very  bad  they  usually 
pour  it  out  on  the  stable-floor.  This  method  is  of  course 
objectionable.  At  many  places  this  milk  is  fed  to  swine 
in  the  hope  that  these  omnivorous  animals  are  not  so  par- 
ticular and  so  receptive  of  contagion.  It  is  doubtless  a  fact 


SOURCES   OF   INFECTION   IN   THE   STABLE.  45 

that  one  of  the  reasons  for  the  wide  distribution  of  tuber- 
culosis may  be  sought  here.*  All  abnormal  milk  ought  to  be 
removed  from  the  stable  and  destroyed  as  soon  as  possible. 

Milk  from  Tuberculous  Cows. — The  most  common  form 
of  diseased  milk  with  us,  which  is  abnormal  when  drawn 
from  the  udder,  is  that  from  tuberculous  cows.  Such  milk 
should  not  be  used  without  being  freed  from  its  infectious 
qualities,  above  all  where  tuberculosis  of  the  udder  is  pres- 
ent. In  the  first  stages  of  tuberculosis  it  is  very  hard  to 
prove  whether  the  milk  has  an  abnormal  composition  or 
not  without  delicate  bacteriological  examinations;  it  still 
has  the  color  and  appearance  of  ordinary  milk,  and  the 
number  of  tubercle  bacilli  in  the  same  is  comparatively 
small.  But  as  the  disease  develops,  the  abnormal  condi- 
tion of  the  milk  can  more  easily  be  discovered  with  the 
naked  eye.  Even  when  the  disease  is  in  its  earlier  stages 
the  milk  assumes  a  somewhat  yellowish  color.  Later  on  it 
grows  thinner  and  less  viscous,  and  a  large  number  of 
slimy,  cheese-like  lumps  may  be  discovered  in  the  same. 
The  color  finally  turns  entirely  yellowish  brown. 

We  are  often  able,  even  in  the  earlier  stages  of  tubercu- 
losis, to  tell  the  abnormal  condition  of  the  milk  from  the 
fact  that  such  milk  does  not  show  an  amphoteric  reaction, 
but  is  alkaline — a  feature  which  is  of  course  the  more  char- 
acteristic the  farther  the  disease  has  progressed.! 

*  Bang  states  (Bull.  4,  Copenhagen  experiment  station,  1885,  22) 
that  at  a  Danish  creamery  where  centrifuge  slime  was  fed  to  swine, 
all  of  these  proved  tuberculous,  and  warns  against  the  use  of  slime 
for  this  purpose  without  its  being  previously  boiled  or  heated  toward 
the  temperature  of  boiling  water.  The  prevalence  of  tuberculosis 
among  swine  in  certain  parts  of  Germany  has  been  attributed  to  this 
system  of  feeding.  (See  Ftlhling's  Landw.  Zeitschrift  1893,  p.  779 ; 
Mikh-Zeitung,  1893,  p.  672.)— W. 

f  Amphoteric  Reaction  of  Milk.— When  drawn  from  the  udder 


46  MODERN   DAIRY    PRACTICE. 

According  to  Bang,  tuberculous  milk  coagulates  at 
75°-85°  C.  In  regard  to  tuberculosis  in  cows,  it  may  fur- 
ther be  mentioned  that  not  all  glands  in  the  udder  are 
necessarily  attacked  by  the  disease  at  one  time.  The 
milk  in  the  sound  glands  has  in  such  cases  been  very  rich 
in  fat,  and  reminded  one  of  cream  in  its  appearance.* 

milk  will  as  a  rule  turn  red  litmus  paper  blue  and  blue  litmus  paper 
red,  i.e.,  give  both  an  acid  and  an  alkaline  reaction.  This  double  re- 
action is  explained  by  the  presence  of  normal  and  acid  alkaline  phos- 
phates and  carbonates  in  the  milk  (Soxhlet).  On  standing  even  for  a 
short  time,  normal  cows'  milk  has  always  an  acid  reaction. — W. 

*  The  subject  of  bovine  tuberculosis  has  been  much  discussed  of 
late  among  dairymen  in  all  parts  of  the  world,  and  its  importance 
has  hardly  been  overestimated.  The  complete  eradication  of  the 
much-dreaded  disease  in  our  country  is  one  of  the  great  dairy  prob- 
lems of  the  age.  Fortunately  we  have  in  the  Tuberculin  test  a 
ready  and  but  rarely-failing  means  of  discovering  the  disease  even 
when  it  is  in  its  early  stages.  Breeders  of  dairy  stock  are  now  be- 
ginning to  sell  their  stock  on  a  guarantee  of  freedom  from  tuber- 
culosis, as  shown  by  the  test,  aud  dairy-farmers  in  buying  new  stock 
should  insist  on  such  a  guarantee — in  justice  to  themselves  as  well 
as  to  their  customers. 

Dairymen  suspecting  tuberculous  animals  in  their  herds  should 
not  fail  to  isolate  suspicious  cases  at  once,  and  to  call  in  a  skilled  and 
careful  veterinarian  to  make  the  test.  For  a  preliminary  examina- 
tion of  the  cows  the  following  schedule  of  manner  of  procedure 
adopted  by  Danish  veterinarians  may  be  of  service  (see  Woodhead, 
"Bacteria  and  their  Products,"  1891,  225). 

a.  "First  of  all  the  submaxillary  glands  are  examined;   these 
are  easily  felt,  and  any  change  is  readily  made  out. 

b.  "  The  glands  at  the  root  of  the  neck  and  those  in  front  of  the 
haunch  bones  are  always  carefully  examined.     The  glands  in  the 
flank  should  be  equal  in  size— about  the  size  of  the  middle  finger, 
aud  not  hard.     Mere  enlargement,  however,  even  when  considerable, 
is  not  looked  upon  as  of  great  importance  if  it  is  perfectly  equal 
on  both  sides. 

c.  "The  animal  is  made  to  cough  by  means  of  pressure  on  the 


SOUECES   OF   INFECTION   IN  THE   STABLE.  47 

Milk  from  Inflamed  Udders. — Another  form  of  diseased 
milk  which  is  also  abnormal  when  drawn  is  that  produced 

windpipe,  and  the  lungs  are  carefully  examined  during  and  after 
the  coughing.  The  condition  of  the  skin  over  the  flanks  is  carefully 
observed  ;  it  should  in  a  healthy  animal  be  'loose,'  like  that  of  a 
clog,  soft  and  pliable  ;  any  adhesion,  hardness,  or  harshness  should 
be  carefully  noted. 

d.  "  The  udder  is  carefully  examined  for  inequality  of  size  or  for 
auy  induration.     It  is  a  somewhat  curious  fact  that  tuberculosis  dis- 
ease usually  affects  the  hind  quarters  of  the  udder,  which  becomes 
hard  and  knotty,  but  not  painful ;  while  in  acute  inflammation  of 
the  udder  the  anterior  quarters  are  quite  as  much  affected  as  the 
posterior  ;  the  pain  is  usually  very  acute,  and  the  process  is  accom- 
panied by  much  more  marked  febrile  symptoms. 

e.  ' '  Then  the  glands  above  the  udder,  high  up  between  the  quar- 
ters, are  most  carefully  examined.    In  cases  of  tubercular  disease  of 
the  udder  these  glands  are  invariably  affected,  are  unequal  in  size, 
and  the  large  one,  corresponding  to  the  affected  quarter,  is  usually 
considerably  indurated. 

/.  "Careful  auscultation  is  carried  out  at  least  once  a  month, 
the  fore  foot  of  the  side  that  is  being  examined  being  always  well 
advanced.  The  normal  expiration-sound  lasts  half  as  long  as  the 
normal  inspiration,  and  if  this  rhythm  is  deviated  from  in  anyway,  a 
further  and  thorough  examination  of  the  lungs  should  always  be 
made. 

g.  "  The  examination  is  continued  still  further  if  the  slightest 
suspicion  of  tubercular  disease  is  aroused  by  the  above  investigation. 
...  In  case  of  suspicion  the  milk  from  that  animal  should  not  be 
put  into  the  milk-supply,  but  is  either  thrown  out  or,  after  being 
most  thoroughly  disinfected  by  prolonged  boiling,  is  given  to  the 
pigs." 

Prof.  Nocard,  of  Alfort  Agricultural  College,  France,  who  has 
made  a  special  study  of  this  subject,  in  a  recent  publication  gives  the 
following  directions  for  manner  of  procedure  in  case  of  the  appear- 
ance of  tuberculosis  in  a  herd  (L' Industrie  Laitiere,  19  (1894),  p.  144) : 

"The  diagnosing  power  of  tuberculin  is  at  the  present  time  ad- 
mitted by  all  authorities.  By  its  application  it  is  easy  to  prevent  the 


48  MODERN   DAIRY   PRACTICE. 

by  cows  suffering  from  inflammation  of  the  udder — a  dis- 
ease which  is  not  transferable  from  cows  to  man,  as  tuber- 
spread  of  tuberculosis  in  cattle.  In  all  cases  where  tuberculosis  has 
been  found  or  is  suspected,  all  animals  in  the  herd  should  be  injected 
with  tuberculin  ;  and  those  giving  the  characteristic  reaction  must  at 
once  be  separated  from  the  sound  ones,  and  a  thorough  disinfection 
of  the  stable  must  take  place.  It  is  not  necessary  to  sacrifice  the 
diseased  cows  immediately ;  their  milk  may  be  utilized  AFTER 
HAVING  BEEN  BOILED,  and  they  may  be  prepared  for  the  butcher, 
so  that  the  owner  may  realize  as  much  as  possible  on  them.  The 
disease  having  been  taken  in  its  beginning — at  least  in  case  of  the 
greater  number  of  animals— they  fatten  easily,  and  the  loss  resulting 
from  sacrificing  them  prematurely  will  thus  be  reduced  to  a  mini- 
mum. Delivered  to  the  butcher  at  the  proper  time  their  lesions  will 
be  insignificant.  [Tubercle  bacilli  very  rarely  appear  in  the  flesh  of 
animals,  and  even  if  such  should  be  the  case  the  bacteria,  according 
to  the  consensus  of  authorities  on  the  subject,  are  easily  killed  by 
simply  boiling. — W.] 

"  The  essential  point  to  be  observed  in  all  cases  is  to  remove  the 
diseased  animals  from  the  healthy  ones,  and  to  exclude  them  merci- 
lessly from  reproduction.  If  the  young  animals  escape  infection 
the  renewal  of  the  herd  will  not  be  endangered,  and  the  void  will  be 
filled  in  the  course  of  a  couple  of  years.  When  I  have  applied 
tuberculin  injections  I  have  always  assured  the  owners  that  the 
young  stock  which  proved  healthy  would  remain  so  in  the  future 
provided  they  were  separated  from  the  diseased  animals ;  and  ex- 
perience has  always  confirmed  the  correctness  of  this  prevision. 

"  It  is  only  necessary  to  go  over  a  herd  once  with  the  test,  if  the 
directions  given  have  been  strictly  followed  ;  no  new  animals  should 
be  introduced  into  the  herd  before  having  been  subjected  to  the 
tuberculin  test. 

"Thanks  to  this  simple  method,  the  owners  of  the  animals 
can  with  little  expense  and  without  relying  on  governmental  aid, 
free  themselves  from  the  heavy  tribute  annually  paid  to  tuber- 
culosis. 

"Everybody  knows,  but  it  is  well  to  repeat  it,  how  dangerous. 


SOURCES   OF  INFECTION  IK  THE   STABLE.  49 

cnlosis,  but,  to  make  up  for  it,  is  the  more  contagious  for 
cows.  As  in  case  of  tuberculosis  it  is  caused  by  bacteria, 
and  has  frequently  been  the  cause  of  large  losses.  We 
may  here  only  recall  the  great  damage  which  it  caused 
in  Holstein,  1873-78,  where,  e.g.,  at  the  estate  "  Stendorf  " 
the  whole  herd  of  200  milch-cows  was  attacked.  As  an 
example  of  the  extremely  contagious  nature  of  the  inflam- 
mation of  the  udder,  the  following  may  be  cited :  During 
the  epidemic  mentioned,  the  dairyman  at  Stendorf  was 
once  called  to  a  remote  farm  where  inflammation  of  the 
udder  had  never  yet  appeared,  in  order  to  assist  in  a  hard 
parturition  case  of  a  cow.  Six  days  after  his  visit  the  first 
case  of  inflammation  of  the  udder  was  observed  at  the 
latter  place,  and  before  long  six  of  the  nine  cows  on  the 
farm  were  attacked.  The  dairyman  had  doubtless  brought 
the  bacterium  causing  the  inflammation  to  this  farm. 
Milk  from  cows  attacked  by  this  disease  may  be  recog- 


tuberculosis  is  to  human  life.  In  banishing  the  disease  from  the 
cow  stables  we  banish  one  of  the  causes  of  its  spreading  among  the 
human  race." 

The  following  publications  contain  the  main  contributions  to 
our  knowledge  of  tuberculosis  in  cattle  in  America  : 

Mass.  (Hatch)  Experiment  Station  Bulletin  No.  8,  April,  1890. 

Maine  Experiment  Station  Report  1890,  pp.  59-64. 

Pennsylvania  Experiment  Station  Bulletin  No.  31,  Oct.  1892. 

Virginia  Experiment  Station  Bulletin  No.  26,  March  1893. 

Ottawa  (Canada)  Central  Experimental  Farm  Bulletin  No.  20. 

Cornell  Experiment  Station  Bulletin  No.  65,  April,  1894. 

Wisconsin  Experiment  Station  Bulletin  No.  40,  July,  1894. 

Report  on  Tuberculosis  in  Ontario  (Bryce),  Toronto,  1894. 

Veterinary  Magazine,  1894,  p,  12. 

Also,  Annual  Reports  of  Bureau  of  Animal  Industry,  U.  S.  Dept. 
of  Agriculture,  Washington,  D.  C.— W. 


50  MODERN    DAIRY    PRACTICE. 

nized  among  other  ways  by  its  appearance,  it  being  thick, 
slimy,  and  mixed  with  lumps.* 

"  Diseased  Milk." — It  is  fortunately  still  rather  seldom 
in  this  as  well  as  other  northern  countries  to  find  the  milk 
which  is  in  any  way  abnormal  when  drawn  from  the  udder. 
Creameries  troubled  with  "  diseased  milk  "  are,  however, 
often  mentioned  in  our  agricultural  literature,  and  cream- 
erymen  usually  account  for  the  poor  quality  of  the  butter 
produced  by  this  reason.  Milk  which  is  abnormal  when 
drawn  may  occasionally  appear  also  on  our  farms,  but 
generally  the  diseases  of  the  milk  met  with  in  our  cream- 
eries and  dairies  have  arisen  because  the  milk  has  been 
subjected  to  a  careless  treatment  after  having  been  drawn. 
Many  dairymen  try  to  hide  their  own  faults  and  careless- 
ness by  speaking  of  diseased  milk,  in  the  same  way  as 
persons  who  do  not  understand  their  business  generally 
lay  the  poor  results  obtained  to  faults  in  the  material  or 
the  tools. 

Light  in  Cow-stables. — If  the  preceding  directions  of 
strict  order  and  cleanliness  during  the  milking  process  and 
in  all  manipulations  on  the  farm  are  to  be  followed,  it  is 
absolutely  necessary  to  have  sufficient  light  in  the  stables, 
especially  during  milking-time.  Most  of  our  stables  leave, 
however,  much  to  be  wished  for  in  this  respect.  This  is 
true  not  only  of  the  previously  mentioned  dark,  prison-like 
cow-stables  so  often  met  with  at  our  smaller  farms,  but  also 
of  many  farms  run  in  a  rational  manner.  It  is  of  great 
importance  to  have  sufficient  light  in  the  cow-stable,  not 
only  for  the  reason  that  the  larger  number  of  bacteria,  and 


*  See  Bang,   "The  Causes  of  Inflammation  of  the  Udder  in 
Cows,"  14th  Report,  Copenhagen  Experiment  Station,  1889,  38  pp. 


SOURCES   OF   INFECTION   IN   THE   STABLE.  51 

those  most  injurious  to  the  dairy  business,  thrive  best  in 
darkness,  as  we  shall  refer  to  later  on,  but  it  is  impossible 
to  clean  the  cows  properly  and  to  conduct  the  milking 
properly  in  a  dusky  stable.  The  cow-stable  must  be  lib- 
erally supplied  with  clean  windows,  and  in  winter-time  it 
must  be  so  arranged  that  the  stable  sball  be  sufficiently 
lighted  morning  and  evening.  If  we  step  into  one  of  our 
common  cow-stables  on  a  winter  evening  at  milking-time, 
we  shall  often  be  surprised  to  note  how  the  milkers  have 
to  grope  around  in  darkness  while  they  perform  their  im- 
portant work  and  handle  a  material  so  delicate  and  easily 
contaminated  as  is  milk.  Under  such  conditions  it  is  not 
strange  if  part  of  the  milk  goes  outside  the  milk-pail  in- 
stead of  into  it,  and  that  the  cows  are  not  always  clean 
when  the  milking  begins.  It  is  therefore  an  absolutely 
necessary  condition  for  the  production  of  milk  that  will 
keep  well  that  the  light  in  the  cow-stables  be  improved; 
every  milker  ought,  furthermore,  to  be  supplied  with  his 
own  bright  shining  lantern. 

Air  and  Bacteria. — As  already  mentioned,  the  impure 
air  in  the  stable  is  one  of  the  main  causes  of  bacterial  in- 
fection of  the  milk  before  it  leaves  the  stable.  There  is 
no  .difficulty  in  proving  this  bacteriologically.  The  fact  is 
apparent  from  the  experiments  above  given  made  in  the 
stable  and  in  the  open  air,  concerning  the  bacterial  infec- 
tion from  the  udder  and  its  surroundings  (p.  28).  Hesse 
states  in  his  account  of  the  quantitative  determination  of 
the  micro-organisms  of  the  air,  that  he  found  not  less  than 
120  bacteria  and  molds  in  a  liter  (quart)  of  air  in  a  common 
cow-stable,  while  the  same  quantity  of  air  in  a  dusty  school- 
room, from  where  the  pupils  were  just  hurrying  out,  con- 
tained only  80  such  micro-organisms.  It  has  been  found 


52  MODERN   DAIRY   PRACTICE. 

by  scientific  investigations  that  bacteria  do  not  multiply  in 
the  air;  they  lack  there  the  moisture  so  essential  for  their 
development.  The  air  can  therefore  be  filled  with  bac- 
teria only  by  the  drying  and  subsequent  reduction  to  a 
powder-like  dust  of  fluids  and  other  media  where  these 
organisms  are  found,  the  dust  being  later  on  set  in  motion 
by  currents  of  the  air.  The  bacteria  of  the  air  are  thus 
closely  connected  with  the  dust,  and  appear  most  numerous 
in  air  where  a  good  deal  of  dust  is  set  in  motion.  When 
the  air  is  not  stirred,  both  bacteria  and  the  dust  will  of 
course  sink  to  the  ground  or  the  floor.  It  has  been  found 
that  the  air  in  a  closed  living-house,  when  left  undisturbed 
will  become  free  from  bacteria,  in  one  to  two  hours. 

During  the  hot  season  the  outside  air  contains  most 
bacteria,  while  during  snowy  winters  it  contains  very  few 
such  in  our  climate.  In  the  atmosphere  of  cities  con- 
siderably more  bacteria  are  usually  found  than  in  the  air 
in  the  country.  On  high  mountains  and  out  on  the  sea 
far  from  land,  or  deep  down  into  the  earth,  the  air  seems 
to  be  sterile. 

Importance  of  Pure  Air. — It  is  evident  that  the  air  in  a 
cow-stable  must  be  highly  infected  with  bacteria  a  large 
portion  of  the  day,  it  being  usually  in  strong  motion  and 
an  enormous  number  of  them  being  scattered  at  feeding- 
time.  As  the  bacteria  obey  the  law  of  gravitation  they  are 
of  course,  as  we  have  seen,  most  numerous  in  the  lower 
layers  of  the  air,  i.e.,  just  where  the  milking  takes  place. 
The  bacterial  content  of  the  atmosphere  in  a  stable  varies, 
however,  greatly  at  different  times  of  the  day,  as  I  have 
often  had  an  opportunity  of  proving  in  my  investigations. 
While  a  sterilized  gelatine  plate  placed  in  the  stable  im- 
mediately after  the  feeding  within  two  minutes  became 


SOURCES  OF  INFECTIOH   IN  THE  STABLE.  53 

seeded  with  innumerable  bacteria,  a  similar  plate  placed 
at  exactly  the  same  spot  two  hours  after  the  feeding  and 
the  cleaning  in  the  stable  was  done,  did  not  become  greatly 
infected  with  bacteria  during  ten  minutes'  exposure.  This 
shows  plainly  that  it  is  possible  to  considerably  decrease 
the  infection  of  the  milk  through  the  air  of  the  stable.  It 
is  only  necessary  for  this  purpose  that  chores  which  con- 
taminate the  air  be  done  with  the  greatest  care,  and  not 
performed  at  the  time  of  or  shortly  before  milking. 

Time  of  Feeding.  On  many  farms  it  is  the  custom  to 
feed  the  cows  directly  before  or  during  milking.  The 
intention  is  to  direct  the  attention  of  the  cow  away  from 
the  milking,  or  to  induce  her  to  stand  quiet  during 
the  process.  It  is,  however,  apparent  that  it  is  not  nat- 
ural for  a  cow  to  eat  while  she  is  being  milked,  from  the 
fact  that  she  stops  eating  when  the  calf  begins  sucking 
her,  and  that  she  never  grazes  in  the  pasture  while  the 
milking  takes  place.  I  do  not  believe  that  feeding  imme- 
diately before  or  during  the  milking  tends  to  keep  the  cow 
quiet.  But  even  if  the  method  should  bring  this  about,  it 
is  nevertheless  to  be  rejected.  Feeding  directly  before  or 
during  the  milking  leads  largely  to  a  contamination  of  the 
milk,  especially  when  the  cows  are  fed  coarse  fodders.* 
Masses  of  dust  with  accompanying  bacteria  are  set  in  mo- 
tion during  the  feeding.  Hesse  states  that  the  air  in  the 
stable  in  his  experiments  contained  so  many  bacteria  and 
especially  molds  when  the  feeding  took  place  that  it  was 
impossible  to  count  them.  In  an  instance  where  very 
rusty  chaff  and  straw  was  fed  in  a  stable  I  found  the  air 


*  Bee  also  Weigmann  and  Zirn,  on  the  source  of  bacteria  in  milk, 
Milch  Zeitung,  22,  (1893)  569;  Exp.  Sta.  Record  5,  p.  431.— W. 


54  MODERN   DAIRY   PRACTICE. 

almost  filled  with  such  micro-organisms.  As  might  be 
predicted,  it  was  easy  to  trace  large  quantities  of  them  in 
the  milk  produced  on  this  farm,  where  the  milking  and 
the  feeding  took  place  at  the  same  time.  The  feeding  in 
many  places  is  also  performed  in  a  manner  most  favorable 
to  the  spreading  of  the  dust,  e.g.,  by  being  thrown  down 
from  the  hay-mow  through  a  chute.* 

We  then  see  that  the  quality  of  the  milk  will  be  greatly 
lowered  by  exposure  to  the  dust  stirred  up  when  the 
fodder  is  brought  into  the  stable  and  fed  to  the  cows. 
The  most  typical  bacteria  in  this  dust  seem  to  be  Bacillus 
subtilis  and  non-peptonizing  forms  resembling  it.  The 
reason  why  these  organisms  are  so  common  in  the  milk 
may  doubtless  be  traced  to  this  origin. 

It  ought  furthermore  to  be  remembered  that  cows  like 
to  take  a  quiet  siesta  after  their  meals,  during  which 
digestion  may  be  allowed  to  go  on  undisturbed.  It  is 
therefore  of  much  importance  that  some  time — at  least 
1J  hours — go  by  after  the  feeding  before  the  milking 
takes  place.  In  this  way  the  animals  will  be  more  at  ease, 
and  the  danger  from  infection  will  be  decreased. 

Regular  Cleaning  of  the  Stable. — A  vicious  practice 
followed  on  many  farms,  which  is  perhaps  more  fatal  than 
the  unfortunate  arrangement  of  feeding  just  mentioned, 
is  that  the  manure  is  cleaned  out  during  or  immediately 
before  the  milking.  It  is  not  difficult  to  see  that  in  clean- 
ing out  the  stable  a  mass  of  small  particles  of  dung  will 

*  Some  feeds,  such  as  turnips,  cabbage,  silage,  etc.,  may  further- 
more be  fed  safely  after  milking,  while  if  fed  before  or  during  milk- 
ing they  will  give  their  peculiar  flavors  to  the  milk.  Complaints  of 
certain  feeds  tainting  the  milk  have  doubtless  in  many  cases  come 
from  an  injudicious  method  of  feeding. — W. 


SOURCES   OF   IKFECTIOK   IN   THE   STABLE.  65 

be  spread  around  in  the  air  and  fall  down  on  the  cows,  on 
the  clothes  and  hands  of  the  milkers,  in  the  milk-pails, 
etc.  The  fact  that  many  of  the  worst  enemies  of  the 
milk  are  included  among  the  bacteria  adhering  to  these 
particles  makes  the  matter  still  worse.  Within  a  short 
time  some  of  them  produce  putrefactive  fermentations  in 
the  milk,  while  others  do  not  show  their  injurious  effects 
until  later  on — viz.,  in  the  products  of  the  milk.  During 
their  presence  in  the  milk  bacteria  of  the  latter  kind 
lie  in  a  torpor-like  inactivity,  from  which  they  do  not 
awake  until  they  find  conditions  more  favorable  to  their 
growth  ;  they  then  obtain  power  to  conquer  other  bacteria 
found  in  the  same  medium,  and  soon  give  rise  to  their 
special  fermentations.  It  ought  to  be  remembered  that 
the  longer  the  manure  remains  in  the  warm  cow-stable,  the 
richer  it  will  be  in  bacteria,  and  above  all  in  spores  of 
bacteria,  and  therefore  the  sooner  it  is  removed  the  better. 
On  some  well-conducted  farms  I  have  seen  this  rule  ob- 
served so  carefully  that  the  manure  has  been  carried  away 
as  soon  as  it  falls  to  the  floor,  an  arrangement  which  can 
be  carried  out  cheaper  than  many  persons  think.  If  the 
principle  taught  cannot  be  so  scrupulously  followed,  it  is 
necessary  to  prevent  as  far  as  possible  the  infection  eman- 
ating from  this  source  by  other  precautions.  The  ma- 
nure should  be  removed  from  the  stable  several  times 
during  the  day,  and  it  must  be  arranged  so  that  a  suffi- 
ciently long  time  will  elapse  between  this  operation  and 
the  milking. 

Dangers  of  Infection  from  Fermenting  Foods. — Another 
quite  common  condition  on  our  farms  which  is  deleterious 
to  the  quality  of  the  milk  is  that  fermenting  or  spoilt 
cattle-foods,  etc.,  are  kept  in  the  stable  or  in  its  immediate 


56  MODERN   DAIRY   PRACTICE. 

vicinity.*  The  milk  may  easily  be  infected  with  very  in- 
jurious bacteria  from  such  hotbeds  of  fermentation. 

Ventilation  in  the  Stable. — As  regards  the  air  in  the 
stable,  it  is  of  the  greatest  importance  to  avoid  as  much  as 
possible  everything  that  may  tend  to  make  it  impure  ; 
the  air  must  be  kept  fresh  and  pure  by  means  of  an 
effectual  and  well-arranged  system  of  ventilation.  The 
stable  ought  to  be  aired  after  each  milking,  and  the  clean- 
ing of  stable  and  feeding  should  not  begin  till  after  the 
milking. 

In  order  that  the  ventilation  be  effective  it  is,  however, 
essential  that  the  air  outside  of  the  barn  be  purer  than 
that  in  it,  which  in  many  places  is  not  the  case.  Gener- 
ally the  surroundings  of  the  cow-stable  are  not  given  the 
attention  and  careful  inspection  which  they  deserve. 

The  fear  that  the  animals  be  exposed  to  draught  must 
not  prevent  the  airing  of  the  stable,  for  draught  can  very 
well  be  avoided  if  the  ventilation  be  arranged  in  a  proper 
manner.  The  ventilation- valves  of  the  stable  ought 
always  to  be  open  except  when  the  temperature  sinks  be- 

*  The  general  use  of  silage  as  a  food  for  dairy  cows  among  Amer- 
ican farmers  makes  this  a  most  important  point  to  us,  which  we 
cannot  afford  to  overlook.  In  building  a  silo  mere  convenience  in 
handling  the  silage  is  too  often  thought  of,  to  the  exclusion  of  con- 
sidering the  influence  of  the  presence  of  a  fermented  cattle-food  on 
the  milk  and  its  keeping  quality.  The  silo  is  often  built  in  a  corner 
of  the  barn,  and  arranged  so  as  to  open  directly  to  the  stable,  filling 
the  stable  air  at  all  times  with  a  strong  silage  odor.  Silage,  and 
especially  corn  silage,  is  one  of  the  great  adjuncts  to  modern  Amer- 
ican dairy-farming,  but  it  is  essential  that  it  be  fed  judiciously,  in 
connection  with  some  dry  coarse  fodders,  hay,  corn  fodder,  etc.,  and 
that  the  feeding  take  place  after,  and  not  directly  before  or  during 
milking.-W. 


SOURCES   OF   INFECTION   IN  THE  STABLE.  57 

low  50°.  Stables  as  a  rule  are  kept  too  warm;  the  high 
temperature  is  not  only  not  beneficial  to  the  cows,  but  on 
the  other  hand  is  highly  favorable  to  bacteria,  the  de- 
velopment of  which  takes  place  with  far  more  intensity  at 
59°-68°  than  at  50°.  By  a  proper  system  of  ventilation 
air  containing  fewer  bacteria  will  get  into  the  stable,  and 
the  multiplication  of  the  bacteria  present  will  at  the  same 
time  be  delayed  and  decreased.* 

*  To  show  more  plainly  that  the  demands  made  as  regards  the 
order  of  work  in  the  stable  are  not  impossible,  the  author  gives  a 
schedule  for  the  day's  work  which  is  in  conformity  with  the  princi- 
ples laid  down.  The  schedule  is  not  applicable  to  our  American 
conditions,  and  is  given  here  mainly  as  a  matter  of  curiosity  to  show 
the  amount  of  work  and  what  length  of  day's  work  the  European 
farm-laborer  is  asked  to  perform. 
"  4  A.M.  Feeding.  Cleaning  out  stable. 

5  A.M.  Cows  watered.     Stable  aired. 

5.30  A.M.  The  udders  of  the  cows  are  cleaned  and  the  milking 
begins. 

7-8.30  A.M.  Stable  closed. 

8.30  A.M.  Feeding.     Cows  cleaned  and  brushed. 

10-11.30  A.M.  Stable  closed. 

11.30  A.M.  Cows  watered. 

12  noon.  The  udders  of  the  cows  washed  and  the  milking  begins. 

1.30  P.M.  Feeding.  Cleaning  out  stable  ;  cows  let  out  and 
stable  aired. 

2.30-4  P.M.  Stable  closed  ;  bulls  let  out. 

4  P.M.  Feeding.     Cows  cleaned  and  brushed. 

5.30  P.  M.  Cows  watered  ;  stalls  carefully  cleaned  and  stable 
aired. 

6  P.M.  The  udders  cleaned  and  the  milking  begins. 
7.30  P.M.  Distributing  night-feed. 

8  P.M.  Stable  closed  for  the  night. 

In  making  the  schedule  of  work  given,  I  have  followed  these 
main  principles : 


58  MODERN    DAIRY   PRACTICE. 

Delay  in  Removing  Milk  from  Stable. — No  matter  how 
carefully  the  precautions  given  concerning  the  treatment 
of  the  milk  are  observed,  the  milk  is  always  threatened 
with  infection  from  many  sources  as  long  as  it  is  in  the 
stable.  The  fact  that  milk  when  drawn  from  the  udder 
has  a  temperature  highly  favorable  to  the  development  of 
the  bacteria,  and  that  it  is  a  splendid  nutritive  medium  for 
the  large  majority  of  bacteria,  makes  the  matter  worse. 
It  is  plain  therefore  that  the  milk  ought  to  be  removed 
from  the  warm  stable  as  soon  as  possible.  On  most  farms 
in  our  country  an  entirely  different  practice  is  followed. 
When  a  cow  has  been  milked  or  the  milk-pail  is  full,  the 
milk  is  poured  into  a  large  transportation-can,  at  the  open- 
ing of  which  a  strainer  is  placed.  As  this  does  not  allow 
the  milk  to  run  through  very  quickly,  and  the  opening  of 
the  can  is  usually  comparatively  small,  the  milk  must  be 
poured  slowly  from  the  pail.  The  milk  is  usually  left  in 
the  can  until  the  whole  herd  has  been  milked,  and  it 
is  then  removed  from  the  warm,  foul  air  in  the  stable. 
This  manner  of  procedure  is  very  deleterious  to  the  quality 

1.  The  manure  is  to  be  cleaned  out  1|  hours  before  rnilking-time 

2.  The  stable  is  aired  every  time  it  is  cleaned. 

3.  The  cows  are  watered  before  every  milking. 

4.  The  feeding  takes  place  at  least  1£  hours  before  milking, 

5.  The  cows  have  a  rest  of  1|  hours  three  times  a  day,  during 
which  time  the  stable  is  closed. 

6.  The  cows  are  cleaned  twice  a  day  ;   their  udders  and  hind 
parts  are  washed  before  every  milking. 

7.  The  cows  are  allowed  to  exercise  during  the  warmest  time  of 
the  day. 

If  the  feeding  takes  place  even  five  times  a  day,  the  demands 
made  in  this  respect  may  be  satisfied.  If  the  number  of  feeds  is 
smaller,  it  is  of  course  still  easier  to  observe  these  principles." 


SOURCES   OF   INFECTION   IN  THE   STABLE.  59 

of  the  milk.  It  is  exposed  to  air  filled  with  all  kinds  of 
contagious  organisms,  and  is  /eft  to  remain  in  the  stable  an 
hour  or  still  longer;  this  is  so  much  the  worse  since  the 
transportation-can  is  often  not  perfectly  clean.  I  am  fully 
convinced  that  diseases  of  milk  with  us  are  most  frequently 
caused  by  irrational  methods  of  procedure  like  those 
mentioned.  Fortunately  it  is  very  easy  to  change  this 
method  so  that  it  becomes,  if  not  perfect,  at  any  rate 
far  better.  First  of  all,  the  milk  must  be  removed  from 
the  stable  as  soon  as  possible.  Further,  the  milk  ought  not 
to  be  strained  in  the  stable,  but  in  a  separate  room  near  by, 
where  the  air  is  pure  and  fresh,  and  where  cleanliness  is 
observed  in  the  most  scrupulous  manner.  Such  a  room 
ought  to  be  found  in  connection  with  every  cow  stable. 
It  must  not  be  placed  in  the  neighborhood  of  the  manure- 
pile,  and  is  to  be  provided  with  large  windows,  but  may 
otherwise  be  built  very  plainly.  It  is  a  good  plan  to 
keep  the  basin  for  washing  of  hands  in  this  room,  so  that 
this  operation  may  be  performed  after  each  cow  has  been 
milked.* 

*  Another  reason  why  the  setting  or  separation  of  inilk  should 
not  be  delayed  more  than  necessary  is  that  delay  will  cause  a  di- 
minished yield  of  butter  from  the  milk,  making  the  skim-milk  richer 
in  fat.  This  has  been  shown  by  a  number  of  experimenters : 

(1)  For  creaming  by  gravity  processes :  by  Fjord,  14th  Report  of 
Dairy  Experiments,  1881,  p.  24;  Henry,  Wis.  Experiment  Station  Re- 
port II.  p.  21;  Wing,  Cornell  Experiment  Station  Bulletin  No.  29; 
Babcock,  Wis.  Experiment  Station  Report  VIII.,  p.  82;  Hills,  Ver- 
mont Experiment  Station  Report  f.  1890,  p.  100;  Robertson,  Canada 
Experimental  Farms,  1891,  p.  89;  Dean,  Ontario  Agricultural  Col- 
ledge  Report  1891,  p.  181;  1892,  p.  219. 

(2)  For  centrifugal  creaming :  by  Fjord  (loc.  cit.)  and  by  Adametz 
and  Wilckens  (Ldw.  Jahrb.  21  (1892),  p.  131;  Exp.  Sta.  Rec.  3,  p. 


60  MODERN  DAIRY   PRACTICE. 

Straining  the  Milk. — As  soon  as  the  milk  is  brought 
into  this  room  it  ought  to  be  strained  through  a  fine 
strainer.  By  straining  the  milk  in  a  room  with  fresh  and 
pure  air,  a  strong  infection  of  bacteria  is  not  only  avoided, 
but  the  advantage  is  also  gained  that  the  milk  is  aired  in 
the  best  manner.  The  animal  odor  of  milk  as  drawn  from 
the  udder,  which  is  so  unpleasant  to  many,  will  not  disap- 
pear to  an  appreciable  extent  if  the  straining  takes  place 
in  the  stable  where  the  air  is  foul;  the  odor  may,  on  the 
contrary,  often  increase  by  the  milk  being  kept  there  for 
any  length  of  time.  In  the  fresh  air  of  the  milk-room 
the  animal  odor  would,  however,  largely  disappear. 

The  straining  of  the  milk  may  cause  germs  of  infection 
to  be  spread  in  the  milk  instead  of  removing  them  from 
the  same — if,  e.g.,  the  strainer-cloth  is  not  changed  often 
enough,  or  if  the  wire  strainer  is  not  frequently  cleaned. 
In  such  cases  it  will  easily  happen  that  the  finest  dust-like 
impurities  remaining  on  the  strainer  are  pressed  downward 
by  the  milk  running  through,  and  that  the  bacteria  found 
on  the  larger  impurities  are  washed  off.  Actual  trials 
have  convinced  me  that  this  may  happen  and  largely 
contribute  to  the  infection  of  the  milk.  I  spread  some 
coarse  soil  strongly  impregnated  with  bacteria  on  a  fine 
strainer  cloth  and  poured  newly-separated  milk  contain- 
ing only  a  small  number  of  bacteria  over  the  same.  The 

652).  The  latter  investigators,  as  it  would  seem,  erroneously  ascribe 
the  diminished  yield  of  butter  in  case  of  delayed  separation  to  the 
transportation,  instead  of  to  the  delay  in  separation  incident  to  the 
same.  Fjord  showed  that  in  the  ice-setting  system  transportation 
gave  even  somewhat  better  results  than  mere  delay  for  the  same 
length  of  time.  Delay  caused  a  greater  decrease  with  the  ice-setting 
system  of  cream-raising  than  with  the  separator. — W. 


SOURCES  OF  INFECTION-  IN  THE  STABLE.       61 

bacteria  in  the  milk  were  previously  studied  and  found 
to  be  different  from  the  characteristic  forms  in  the  layer 
of  soil.  After  the  straining  the  milk  showed  an  entirely 
different  appearance  under  the  microscope  than  before. 
It  now  teemed  with  the  same  kinds  of  bacteria  as  those 
found  in  the  soil.  In  a  sample  taken  after  the  straining 
had  continued  for  some  time  their  number  had,  however, 
greatly  decreased,  and  soon  the  strained  milk  contained  the 
same  kinds  of  bacteria  as  the  unstrained  milk,  which 
plainly  showed  that  the  soil  particles  had  lost  their  high 
bacterial  content.  By  a  bacteriological  analysis  of  the 
layer  of  soil  this  proved  to  be  the  case,  as  this  now  con- 
tained only  a  very  small  number  of  bacteria.  The  strained 
milk  was  therefore  far  richer  in  bacteria  than  before  the 
straining,  and  the  keeping  qualities  of  the  milk  were  de- 
creased by  the  straining  process.  We  thus  see  that  by 
carelessness  in  straining  germs  of  infection  may  be  scat- 
tered in  the  milk.  The  large  impurities  are  removed 
from  the  milk  in  the  straining,  but  the  most  dangerous 
components  of  these,  the  fermentation- starters  themselves, 
are  washed  into  the  strained  milk. 

It  is  therefore  very  important  to  change  the  strainer 
cloth  often  during  the  straining;  or,  if  a  metal  strainer  is 
used,  the  operation  should  be  changed  occasionally  by  al- 
lowing steam  or  hot  water  to  pass  through  the  strainer  in 
the  opposite  direction.  The  more  unclean  the  milk  the 
more  frequently  the  changing  and  cleaning  process  should 
take  place. 

In  my  straining  experiments  it  was  also  shown  that  the 
more  violently  the  milk  dropped  on  the  strainer,  the  more 
the  strained  milk  was  mixed  with  fine  soil-particles  and 
cowbairs.  The  kind  of  strainer  used  also  played  an  im- 


62  MODERN    DAIRY    PRACTICE. 

portant  part  in  regard  to  the  quality  of  the  milk  strained. 
Milk  of  highest  purity  was  not  obtained  by  straining  the 
milk  through  a  good  linen  strainer-cloth,  or  by  applying 
a  fine  wire-gauze  strainer,  'but  by  placing  the  linen  cloth 
on  the  wire-gauze  strainer  and  allowing  the  milk  to 
pass  through  them  both.  By  changing  the  former  as 
often  as  need  be,  the  washing-down  of  bacteria  from  the 
filth  remaining  on  the  strainer  will  be  limited  as  much  as 
possible. 

Hauling  the  Milk. — When  the  milk  is  strained  it  should 
as  quickly  as  possible  be  removed  to  the  dairy  or  creamery 
for  further  treatment.  If  the  greatest  care  has  been  taken 
in  cleaning  the  cans,  in  milking  and  other  manipulations 
in  the  stable,  the  milk  in  the  cans  will  be  only  slightly 
infected  by  bacteria.  If  the  milk  is  left  for  a  longer  time 
in  wholly  or  partly  closed  transportation-cans  and  allowed 
to  retain  its  warm  temperature,  the  fruits  of  all  preceding 
efforts  will  be  destroyed.  The  bacteria  in  the  milk  will 
in  such  case  begin  to  multiply  rapidly,  and  the  milk 
will  soon  be  as  highly  infected  as  if  no  precautions 
whatever  had  been  taken  in  the  stable.  It  is  not  yet 
possible  at  this  stage  to  tell  by  test  or  smell  that  the 
bacteria  have  begun  to  start  injurious  fermentations  in 
the  milk;  but  the  results  will  be  felt  in  the  manufacture  of 
the  milk. 

If  the  creamery  is  near  by  the  farm  the  milk  ought  at 
once  to  be  hauled  rapidly  there,  while  in  the  opposite  case 
it  is  necessary  to  take  proper  steps  before  the  transporta- 
tion to  check  the  growth  of  the  bacteria.  The  best  means 
at  our  service  for  this  purpose  is  to  cool  the  milk. 

Cooling  the  Milk. — If  the  cooling  is  conducted  in  the 
right  way  a  strong  current  is  started  in  the  milk-can,  so 


SOURCES  OF   INFECTION   IN   THE   STABLE.  63 

that  the  last  traces  of  animal  odor  may  disappear,*  pro- 
vided only  that  the  can  has  not  too  small  an  opening.  The 
cooling  has,  however,  still  more  important  results.  If  the 
temperature  of  the  milk  is  lowered  sufficiently,  the  de- 
velopment of  bacteria  will  be  completely  stopped.  The 
low  temperature  places  these  organisms  in  a  torpid  condi- 
tion, during  which  they  are  unable  to  multiply  or  to  bring 
about  fermentations.  A  proper  cooling  of  the  milk  will 
therefore  greatly  increase  its  keeping  quality.  By  lowering 
the  temperature  to  45°  F.  (7°  0.),  satisfactory  results  may 
be  obtained ;  but  it  is  safest  in  all  cases  to  cool  to  a  tempera- 
ture of  39°  F.  (4°  0.). 

If  the  milk  is  to  be  hauled  to  a  creamery  not  too  far 
away,  where  it  will  be  immediately  cooled  further  or 
separated,  it  is  not  necessary  to  cool  below  50°  F.  (10°  C.). 
At  this  temperature  the  activity  of  the  bacteria  is  generally 
stopped,  and  the  small  increase  that  may  happen  during 
the  short  interval  will  not  cause  any  damage  worth  men- 
tioning, especially  if  the  milk  is  protected  from  being 
heated  during  the  transportation.  Even  a  cooling  to  about 
54°  F.  (12°  C.)  has  often  proved  of  great  advantage. 

The  matter  will,  however,  stand  differently  if  the  milk 
has  to  be  hauled  far,  and  if  it  is  not  protected  from  heat- 
ing during  the  transportation.  The  cooling  must  then  be 

*  It  lias  been  claimed  that  a  simple  aeration  of  the  milk  will  have 
a  beneficial  effect  on  its  keeping  quality  but  this  is  erroneous,  as 
shown  by  Cooke  (Vermont  Experiment  Station  Report  1892,  p.  127) 
and  Wing  (Cornell  Experiment  Station  Bulletin  No.  39;  Powell 
Aerator).  Aeration  with  cooling,  on  the  other  hand,  will  increase 
the  keeping  quality  of  the  milk;  see  Wing,  loc.  cit;  Plumb  (Purdue 
Experiment  Station  Bulletin  No.  44);  Hills  (Vermont  Experiment 
Station  Bulletin  No.  27) ;  Armsby,  Waters,  and  Caldwell  (Pennsyl- 
vania Experiment  Station  Bulletin  No.  20).— W, 


64  MODERN   DAIRY   PRACTICE. 

considerably  stronger.  The  most  important  point  in  the 
cooling  of  the  milk  is,  however,  that  it  should  take  place 
as  quickly  as  possible.  The  object  of  the  cooling  is  only 
partly  reached  if  the  temperature  of  the  milk  is  not 
rapidly  lowered  to  the  degree  which  has  been  found  prefer- 
able under  the  conditions  of  transportation  present. 

Coolers. — Several  kinds  of  apparatus  for  the  rapid  cool 
ing  of  milk  are  sold.*     Lawrence's  cooler  is  best  known 
(Fig.  20).     It  seems  to  me,  however,  it  exposes  the  milk 


FIG.  20. — LAWRENCE  COOLER. 

too  much  to  infection  from  the  air,  etc.     In  this  respect 
PfeifFs  cooler  (Fig.  21)  offers  greater  safety,  but  it  has  the 

*  The  following  coolers  and  aerators  are  the  main  ones  on  the 
American  market:  "Star  Milk  and  Cream  Cooler,"  "Champion 
Milk  Cooler  and  Aerator,"  "Howard's  Patent  Milk  Cooler," 
"Powell  Aerator."  Dealers  in  dairy  supplies  will  doubtless  be 
glad  to  quote  prices  and  give  any  other  information  desired  con- 
cerning these  and  other  kinds  offered  for  sale. 


SOURCES   OF   INFECTION    IN   THE   STABLE.  65 

disadvantage  of  being  difficult  to  keep  clean.  The  milk 
is  cooled  in  tank  A  by  means  of  crushed  ice  placed  in  the 
outside  tank  B.  As  shown  in  the  figure  the  milk  is  run 
through  pipes  and  between  cooled  tin  surfaces,  and  runs 
into  the  transportation-can  at  the  other  end.  Other 
coolers  will  be  mentioned  later  on  under  "Pasteurization 
of  Milk." 

It  must  be  emphasized  that  the  cooling  in  no  way  may 
take  place  in  the  stable,  although  it  is  stated  in  some  text, 
books  on  dairying  that  this  may  very  well  be  done. 

We  must  not  forget,  however,  that  the  bacteria  are  not 


FIG.  21. — PFEIFF'S  COOLER. 

killed  by  a  simple  cooling  of  the  milk.  When  they  again 
come  under  favorable  conditions  they  at  once  begin  their 
activities.  This  fact  every  dairy  and  creamery  man  must 
always  keep  in  mind  during  the  continued  treatment  of 
the  milk.  If  the  milk  is  subjected  to  a  process  of  manu- 
facture it  must  of  course  have  the  temperature  most 
suited  for  the  different  manipulations,  but  when  left  to 
itself  the  milk  should  always  be  kept  as  cool  as  the  condi- 
tions will  permit. 


66  MODERN   DAIRY    PRACTICE. 

When  to  Cool  the  Milk.  —  Among  our  farmers  and 
milk-dealers  there  is  a  general  belief  that  cooling  is  neces- 
sary only  during  the  hot  season — an  opinion  to  which  I 
most  emphatically  take  exception.  It  is  possible  during 
the  cold  season  to  haul  the  milk  even  to  a  somewhat 
distant  creamery  without  previous  cooling  and  keep  it 
sweet;  but  the  development  of  the  bacteria  will  not  be 
sufficiently  checked  by  this  method.  The  results  do  not 
appear  at  once,  but  are  felt  later  on,  as  the  products  made 
from  the  milk  will  not  keep  well. 

A  quick  and  efficient  cooling  of  the  milk  is  a  strong 
remedy  to  regulate  and  counteract  the  development  of 
the  bacteria  found  in  it.  It  is  my  opinion  that  high- 
grade  dairy  products  can  only  be  made  on  farms  where 
sufficient  quantities  of  ice  are  used  in  the  handling  of  the 
milk.  Fortunately  for  our  country,  nature  has  arranged 
matters  so  that  ice,  the  most  effective  and  practical  means 
of  cooling  the  milk,  is  offered  in  sufficient  quantities  and 
at  a  low  cost  to  our  dairymen. 

The  Value  of  Ice  to  the  Dairyman. — In  this  very  con- 
dition lies,  in  my  opinion,  the  secret  of  the  fact  that  we  in 
this  country,  far  away  from  the  markets  of  the  world,  can 
compete  successfully  in  dairying  with  other  countries 
more  fortunately  situated  as  regards  location  and  many 
other  conditions.  For  instance,  the  ice  in  Denmark  is 
both  expensive  and  poor,  and  cannot  every  year  be  ob- 
tained in  anything  like  sufficient  quantities.  Our  con- 
ditions are  entirely  different.  Our  numerous  lakes  and 
streams  yield  ice  in  abundance.  The  hauling  of  it  does 
not  come  high,  and  the  quality  of  the  ice  leaves  nothing 
to  be  wished  for.  Crystal-clear  lake  ice,  more  than  two  feet 
thick,  of  such  purity  that  it  leaves  practically  no  sediment 


SOURCES   OF   INFECTION   IN  THE   STABLE.  67 

on  melting,  is  obtained  here  every  winter.  In  Denmark, 
and  still  more  in  France  and  Ireland,  which  three  coun- 
tries, besides  Sweden,  are  our  only  competitors  in  the  Eng- 
lish market,  the  dairymen  are  generally  forced  to  cool  the 
milk  with  water  only — a  method  which  doubtless  is  better 
than  no  cooling  whatever,  but  which  does  not  form  any 
certain  remedy  against  bacterial  development.  I  have 
often  had  occasion  to  observe  at  Danish  cooperative 
creameries  that  the  milk  even  on  arrival  at  the  creamery 
has  been  somewhat  sour  or  at  least  has  been  slightly  off 
flavor,  and  that  the  butter  when  packed  in  the  tubs  has 
been  soft  and  insipid — all  a  result  of  deficient  cooling. 
More  than  once  I  have  witnessed  that  the  dairyman  even 
on  large  Danish  estates  has  been  entirely  at  his  wit's  end 
for  lack  of  means  of  cooling  in  the  dairy.  The  Danes 
are  fully  aware  of  the  importance  of  keeping  the  dairy 
products  at  a  low  temperature,  but  the  only  practical 
means  which  would  make  this  possible — the  ice — is  often 
not  to  be  had  at  a  reasonable  price.  If  we  consider  that 
ice-famines  may  as  a  consequence  arise  even  at  the  large, 
financially  strong  proprietary  creameries,  it  is  evident  that 
co-operative  creameries  cannot  require  their  patrons  to 
cool  their  milk  immediately  after  the  milking.  The  milk, 
which  usually  is  hauled  to  the  creamery  only  once  a  day, 
is  at  best  cooled  with  water,  but  is  oftener  exposed  to  a 
very  doubtful  "  air-cooling."  The  result  is,  of  course,  that 
a  perceptible  fermentation  may  often  be  discovered  in  the 
milk  on  its  arrival  at  the  creamery.  And  from  a  second- 
grade  raw  material  no  one  can  make  high-grade  products. 
One  of  the  main  reasons  for  the  rather  low  price  of  Danish 
butter  during  certain  seasons  of  the  year  must  be  sought 
in  these  conditions. 


68  MODERN   DAIRY   PRACTICE. 

Our  dairymen  and  milkmen  may  draw  many  useful 
lessons  from  these  facts.  Ice  can  in  our  climate  easily  be 
kept  packed  in  sawdust.  Small  milk  producers  who  can- 
not make  use  of  large  quantities  may  join  with  one  another 
in  hauling  and  keeping  the  ice. 

Mixing  Evening  and  Morning  Milk. — In  this  connec- 
tion I  will  mention  a  mistake  often  made,  viz.,  to  mix  the 
warm  morning  milk  with  the  cold  evening  milk  before 
the  hauling.  The  whole  quantity  may  be  spoiled  by  this 
practice,  as  a  temperature  especially  adapted  to  the  growth 
of  certain  bacteria  may  under  these  conditions  arise.  If 
the  comparatively  warm,  mixed  milk  be  hauled  a  good 
distance  to  the  creamery  in  the  heat  of  the  sun,  it  is  not 
strange  that  it  is  changed  on  the  arrival  there,  or  at  least 
contains  a  large  number  of  bacteria  the  injurious  effects  of 
which  it  is  hardly  possible  to  overcome  in  the  manu- 
facture of  the  products.* 

The  milk  ought  of  course  to  be  protected  against  heat- 
ing during  the  transportation,  a  rule  which  is  often 
violated.  If  it  has  to  be  transported  a  long  distance,  the 
milk  ought  to  be  cooled  during  the  hauling,  or  ought 
otherwise  to  be  pasteurized  before  shipping.  (See  under 
Pasteurization  of  Milk.) 

Care  of  Milk-pails. — A  very  common  and  strong  in- 
fection of  the  milk  which  takes  place  both  in  the  stable 
and  the  dairy  is  the  one  caused  by  carelessly- cleaned  milk 
pails  and  cans.  Even  the  first  vessel  which  holds  the 
milk  when  drawn  from  the  udder,  the  milk-pail,  usually 
leaves  much  to  be  wished  for  as  far  as  cleanliness  is  con- 
cerned. At  many  farms  in  the  old  countries  wooden  pails 

*The  churning  of  the  milk  which  often  takes  place  in  hauling 
long  distances  is  easily  avoided  by  filling  the  cans  completely. 


SOURCES  OF  INFECTION  IK  THE  STABLE.  69 

are  still  used  for  milking.  Such  pails  are,  however,  en- 
tirely unfit  for  this  purpose,  since  all  kinds  of  bacteria 
very  easily  lodge  in  them.  By  daily  steaming,  etc.,  it  is 
certainly  possible  to  prevent  bacterial  growth  from  gain- 
ing ground,  but  wooden  vessels  can  hardly  stand  daily 
steamings;  they  will  soon  begin  to  leak.  In  case  this  cum- 
brous cleaning  process  is  not  carried  on  most  carefully, 
irregularities  will  soon  appear  in  the  milk  or  its  products 
pointing  to  a  strong  bacterial  infection.  It  is  therefore 
essential  to  use  tin  pails,  which -may  easily  be  kept  free 
from  dirt  with  its  accompanying  bacteria. 

Even  on  well-kept  farms  the  practice  of  leaving  the 
milk-pails  in  the  pasture  is  often  met  with  in  summer- 
time.* Instead  of  bringing  them  home  to  the  dairy  to  be 
cleaned,  they  are  rinsed  in  the  pasture  in  some  stream  or 
lake  and  are  then  turned  upside  down  on  a  fence-post  to 
dry  in  the  air.  By  this  practice  the  pails  are  withdrawn 
from  the  careful  supervision  which  the  farmer  himself  or 
his  superintendent  may  give  to  them  when  kept  at  the 
farm,  and  the  pails  are  not  thoroughly  scoured  and  cleaned 
during  the  whole  summer.  In  corners  of  milk-pails  cleaned 
in  the  manner  given  and  kept  in  the  pasture  I  have  found 
a  slimy  creamlike  substance  resembling  coagulated  milk. 
When  the  substance  was  shown  to  the  dairymaid  she  was 
greatly  surprised  and  could  not  understand  how  so  much 
milk  could  remain  in  the  pail.  By  closer  inspection  this 
whole  whitish  mass  proved  to  be  nothing  but  molds  and 
bacteria.  They  had  presumably  daily  fed  on  insignificant 
milk-remnants  and  strongly  multiplied  in  the  summer  heat. 

*  On  dairy  farms  in  northern  Europe,  during  the  summer  months, 
the  cows  are  usually  milked  in  the  pasture  or  in  an  enclosure  of  the 
same. — W. 


70  MODERH   DAIRY   PRACTICE. 

At  other  farms  the  milk-pails  are  kept  in  the  cow 
stable.  The  inadvisability  of  this  method  ought  to  be 
easily  seen  by  everybody.  The  air  in  the  stable  is  seldom 
so  pure  that  the  pails  will  not  be  highly  infected  there. 
Their  cleaning  will  furthermore  always  be  more  or  less 
deficient  under  these  conditions.  It  is  not  sufficient  that 
the  milk-pails  are  rinsed  and  scrubbed  each  time  they 
have  been  used ;  they  must  first  be  rinsed  in  cold  water 
and  then  scrubbed  with  a  brush  and  boiling  hot  water. 
By  cleaning  first  with  cold  water,  the  milk  remaining  is 
removed  from  the  corners  and  joints;  if  water  above  70°  C. 
is  first  used,  some  of  the  albuminoids  of  the  milk  are 
coagulated  and  will  remain  in  the  corners,  from  where  they 
later  can  be  removed  with  difficulty;  such  coagulated 
albuminoid  substances  are  of  course  splendid  nutritive 
substrata  for  the  bacteria. 

The  Use  of  Soda  in  Cleaning  Milk-vessels. — In  many 
places  it  is  the  custom  to  use  boiling  water  to  which 
soda  has  been  added,  for  cleaning  the  milk-pails.  The 
use  of  such  a  caustic  is,  however,  not  to  be  recommended ; 
it  only  neutralizes  or  hides  the  acid  that  may  be  there,  for 
that  particular  time,  but  does  not  expel  the  causes  of  the 
appearance  of  this  acid.  Kinsing  with  water  containing 
soda  may,  on  the  contrary,  have  injurious  effects,  as  even 
after  last  treatment  with  ordinary  water  some  lye  may 
remain  in  the  corners  of  the  pails  and  make  these  remains 
a  still  better  nutritive  medium  than  the  moisture  remain- 
ing after  rinsing  with  ordinary  water.  Soda  should  there- 
fore not  be  used  indiscriminately  for  cleaning  dairy  uten- 
sils, but  only  in  case  of  vessels  in  which  sour  whey,  etc., 
has  been  kept.  In  using  water  containing  soda  the  last 


SOURCES   OF   INtfECTlOtf   IN   THE   STABLE.  71 


traces  of  the  soda  must  be  removed  by  repeated  rinsings 
with  common  water. 

It  is  a  very  good  plan  to  dip  the  milk-pail  in  boiling-hot 
water  at  the  end  of  each  cleaning.  This  will  make  the  pails 
dry  almost  instantaneously,  even  in  the  joints,  and  a  large 
number  of  bacteria  but  little  tenacious  of  life  (like,  e.g., 
the  one  causing  the  milk  and  butter  disease  at  Duelund 
mentioned  before,  see  p.  20)  will  be  destroyed.  It  is  also 
advisable  to  steam  the  pails  once  a  week,  especially  in 
winter. 

The  milk-cans  used  for  hauling  ought  to  be  treated  in 
the  same  manner  after  each  use,  with  the  difference  that 
steaming  ought  to  be  obligatory  in  their  cleaning.  Steam- 
ing is  the  strongest  weapon  against  bacterial  growth  in  the 
cans  and  should  be  applied  far  more  than  is  now  the  case. 
By  the  word  cleanliness  we  do  not  understand  the  same 
now  as  in  former  days.  In  it  is  included  all  that  heretofore 
was  included  under  the  term  and  a  new  point  has  been 
added  —  freedom  from  bacteria:  cleanliness  now  also  in- 
cludes sterility.  Absolute  sterility  can  of  course  never  be 
reached  in  a  business  like  practical  dairying,  but  it  is 
nevertheless  the  duty  of  every  dairyman  to  try  to  reach  a 
certain  degree  of  sterility  in  the  milk  cans  and  pails  which 
may  be  easily  obtained  in  any  modern  creamery  by  means 
of  steaming. 

Steaming  Milk-vessels.  —  A  good  method  of  arranging 
the  steaming  is,  e.g.,  to  conduct  one  or  two  steam-pipes 
under  the  floor  or  under  a  low  table  near  the  sink  by  an 
arrangement  like  that  shown  in  the  accompanying  illustra- 
tion (Fig.  22). 

When  the  milk-can  has  been  scrubbed  clean,  it  is 
turned  upside  down  over  the  steam-pipe  and  steam  is 


72 


MODERN   DAIRY   PRACTICE. 


turned  on.  In  this  way  all  cans  may  be  easily  and  rapidly 
steamed  and  practically  sterilized.  If  absolute  sterilization 
is  wanted,  it  can  be  obtained  more  easily  by  repeating  the 
steaming  a  couple  of  times  with  short  intervals  than  by 
one  uninterrupted  long  steaming.  "When  the  milk-cans 
have  been  steamed,  they  are  left  upside  down,  unless  cov- 


FIG.  22. — ARRANGEMENT  FOR  STEAMING  MILK-CANS. 

ered  by  a  lid,  until  they  are  to  be  filled  again.  This  is 
to  prevent  the  introduction  of  bacteria  into  the  cans,  the 
bacteria  being,  as  before  mentioned,  subject  to  the  law  of 
gravitation. 

The  steaming  of  the  milk-cans  can  usually  take  place 
only  at  creameries,  as  the  proper  facilities  are  lacking  on 


SOURCES  OP  INFECTION  Itf  THE   STABLE.  73 

the  farms.  If  the  steaming  is  done  by  means  of  a  number 
of  pipes  according  to  the  plan  shown  in  the  illustration, 
the  operation  spoken  of  will  not  take  long. 

As  the  patrons  of  a  creamery  take  back  their  skimmed 
milk  immediately  after  the  separation  it  is  not  usually 
practical  to  steam  the  cans  in  the  creamery.  In  that  way 
one  of  the  most  effective  means  of  securing  good  milk  is 
not  taken  advantage  of,  however.  To  get  his  milk-cans 
steamed  every  patron  should  bring  some  extra  cans  along, 
and  they  may  then  in  turn  be  left  in  the  creamery  to  be 
thoroughly  cleaned  and  steamed. 

This  does  not  imply,  however,  that  the  cans  are  not 
also  to  be  cleaned  at  the  farm  as  well  as  the  conditions 
will  permit.  The  Swedish  writer  K.  F.  Lundin  gives  in 
his  book,  "  The  Main  Conditions  for  Furnishing  Good 
Milk  to  the  Creameries,"  a  sad  but  true  picture  of  how 
bad  matters  generally  stand  in  this  respect.  Although 
intended  for  Swedish  conditions,  his  description  may 
equally  well  be  applied  to  our  country.  He  says  among 
other  things: 

"  Almost  daily  the  author  while  on  duty  has  had  occa- 
sion to  notice  how  milk-cans  are  left  at  railway  depots,  at 
roadsides  and  crossroads,  with  closed  covers,  often  in  the 
full  heat  of  the  sun  the  whole  day  until  evening,  although 
the  farms  often  do  not  lie  more  than  a  stone's  throw  from 
the  place,  and  the  cans  might  easily  be  brought  over  and 
cleaned.  Such  a  practice  cannot  be  called  anything  but 
unpardonable  carelessness  and  gross  negligence.  The  re- 
sults are  soon  felt.  It  is  almost  impossible,  even  by  the 
most  careful  cleaning,  to  remove  the  foul  smell  which 
arises  in  the  cans  when  thus  kept  covered  in  the  heat  of  the 
sun.  The  milk  remaining  in  the  can  from  the  creamery 


74  MODERN   DAIRY   PRACTICE. 

has  soured  and  dried  solid  on  account  of  the  heat,  for 
which  reason  the  cleaning  is  made  greatly  more  difficult 
and  perhaps  not  with  the  best  of  intentions  thoroughly 
effected  in  the  hurry,  since  people  often  do  not  remember 
to  clean  the  cans  till  the  very  moment  when  again  they 
are  to  be  used.  There  is  no  time  to  more  than  just  rinse 
the  can  and  rush  around  its  inside  with  an  old  dish-rag 
which  is  sometimes  dirtier  than  the  can  itself,  having 
often  before  been  used  for  the  same  purpose.  This  is 
not  exaggerated,  but  is  often  met  with  in  practice,  I  am 
sorry  to  say.  The  farmer  himself  may  be  ignorant  of  the 
manner  in  which  the  cans  are  taken  care  of,  but  he  has 
careless  servants  and  does  not  exercise  sufficient  super- 
vision over  them.  When  the  milk  is  poured  into  such 
vessels  one  cannot  be  surprised  if  it  is  damaged  and  comes 
to  the  creamery  in  a  diseased  condition. 

"  At  many  creameries  we  have  also  had  occasion  to  see 
that  there  are  patrons  whose  milk  is  sour  and  bad-flavored 
on  its  arrival  at  the  creamery.  It  ought  not  to  be  harder  for 
these  than  for  the  rest  to  keep  the  milk  sweet.  The  whole 
fault  lies  in  the  lack  of  cleanliness.  Therefore  the  best  way 
to  remedy  the  evil  is  mercilessly  to  send  back  such  milk. 

"If  the  milk-cans  are  examined  more  closely  and  the 
hand  brought  around  in  them,  we  shall  in  some  cases  find 
a  greasy,  yellowish  and  putrid  substance,  an  evident  proof 
of  the  manner  in  which  the  cans  are  kept  clean." 

Annual  Cleaning  of  Stable. — Besides  the  careful  clean- 
ing explained  in  the  preceding,  which  must  take  place 
daily  on  the  farm,  a  thorough  cleaning  combined  with  dis- 
infection should  be  made  at  least  once  a  year.  In  this 
process  the  whole  stable  must  first  be  emptied  and  all 
remnants  of  fodders,  manure,  litter,  etc.,  be  carried  away. 


SOURCES  OF   INFECTION   IN  THE   STABLE.  75 

The  whole  stable  is  then  to  be  scraped  clean  and  swept, 
all  hooks  and  corners,  all  joints  in  walls  and  floor;  the 
ceiling  is  freed  from  dust  and  cobwebs  by  means  of  a  stiff 
broom.  The  sweepings  are  at  once  to  be  removed  from 
the  vicinity  of  the  stable  and  either  burned  (this  is  essen- 
tial if  any  contagious  disease  has  appeared  in  the  herd 
during  the  year)  or  else  ploughed  under  in  the  field.  They 
ought  never  to  be  left  uncovered  near  the  stable,  e.g.,  on 
the  compost  heap  outside  the  same,  for  in  this  case  the 
same  filthiness  filled  with  bacterial  life  may  again  enter 
the  stable  or  else  be  introduced  to  the  living-houses,  etc. 

The  ceiling,  floor,  and  walls  in  the  stable  having  been 
scraped  clean,  both  they  and  the  tools  ought  to  be  care- 
fully scoured  and  finally  rinsed  with  boiling-hot  water; 
small  pools  of  water  possibly  remaining  in  recesses  must 
be  well  wiped  up. 

If  a  mow  for  keeping  coarse  fodders,  etc.,  is  found  in  the 
stable  it  should  also  be  emptied  and  cleaned  every  spring. 

Whitewashing  the  Stable. — If  no  contagious  diseases 
have  appeared  among  the  cattle  in  the  stable  since  the  last 
general  cleaning,  disinfection  of  the  stable  is  not  abso- 
lutely necessary.  After  the  cleaning,  the  inside  of  the 
stable  should  be  at  once  whitewashed.  To  prepare  milk  of 
lime  100  parts  (by  weight)  of  quick-lime  are  mixed  with  60 
parts  of  water,  and  a  quart  of  the  powder-like  slaked  lime 
is  then  mixed  with  5  quarts  of  water.  The  milk  of  lime 
is  well  stirred  before  being  applied.  Walls  and  ceilings, 
pillars,  etc.,  are  brushed  with  lime-water,  an  effort  being 
made  to  have  it  soak  into  cracks  and  corners  as  much  as 
possible.  By  this  whitewash,  which  is  very  cheap,  sev- 
eral advantages  are  gained :  the  stable  becomes  lighter  and 
more  cheerful,  the  woodwork  is  preserved,  and,  what  is 


76  MODERN   DAIRY   PRACTICE. 

still  more  important,  the  development  of  micro-organisms 
is  checked  for  some  time,  as  the  lime-water  acts  as  a  weak 
antiseptic.  To  become  very  effective  the  whitewash  ought, 
however,  to  be  repeated  during  the  summer. 

Disinfection  of  Stable. — In  case  contagious  diseases 
have  appeared  in  the  stable  since  the  last  thorough  clean- 
ing took  place,  or  if  the  milk  in  spite  of  all  precautions 
has  still  proved  strongly  infected  in  the  stable,  the  liming 
ought  to  be  preceded  by  a  disinfection  of  the  stable.  This 
may  be  effected  in  various  ways.  I  shall  here  describe  a 
method  in  use  at  an  estate  in  Germany  which  is  reported 
to  have  given  good  results. 

After  having  scrubbed,  cleaned  and  aired  the  stable, 
as  directed,  all  doors,  wickets,  windows,  flues,  etc.,  are 
shut.  If  straw  or  hay  is  found  in  the  mow  it  must  be 
removed.  The  less  leaky  the  doors,  etc.,  are  the  better. 
Several  earthenware  plates  with  chloride  of  lime  are  now 
placed  in  the  stable  and  crude  muriatic  acid  poured  over 
them.  Chlorin  gas  is  then  generated,  which  will  kill  the 
bacteria.  It  must  be  remembered  that  this  gas  is  injurious 
also  to  man,  especially  for  the  respiratory  organs,  for  which 
reason  one  must  leave  the  stable  as  quickly  as  possible 
after  the  addition  of  the  acid;  the  stable  is  now  kept  shut 
up  for  twenty-four  hours  and  then  thoroughly  aired.  If 
the  stable  is  well  closed  an  application  of  one  pound  of 
chloride  of  lime  and  three  pounds  of  crude  acid  may  suffice 
for  every  5000  cubic  feet.  After  airing,  all  woodwork,  as 
window-sills,  mangers,  beams,  etc.,  are  carefully  scrubbed 
and  washed  with  boiling-hot  water. 

Sulphurous  acid,  which  is  generated  by  burning  sulphur 
in  a  suitable  dish,  has  also  been  used  for  disinfection  of 
stables;  it  acts  only  in  the  presence  of  moisture.  Recent 


SOURCES   OF   INFECTION   IN   THE   STABLE.  77 

investigations  have  shown,  however,  that  the  disinfecting 
power  of  this  agent  is  small  even  if  it  is  allowed  to  act  for 
a  long  time. 

It  is  to  be  remembered  that  disinfection  with  chlorin 
is  generally  more  effective  than  an  application  of  any  dis- 
infecting fluid,  since  the  gas  will  be  able  to  penetrate  into 
all  the  small  cracks  and  crevices. 

The  disinfection  described  is  best  made  in  the  spring, 
soon  after  the  cows  are  let  out  on  pasture.  The  wood- 
work will  then  soon  dry,  and  the  whole  summer  may  be 
taken  for  the  perfect  airing  of  the  stable — an  operation 
which  must  not  be  neglected  even  if  no  disinfection  is 
made.  If  the  stable  is  provided  with  a  wooden  floor,  some 
floor-planks  should  be  taken  up,  so  as  to  facilitate  the 
drying  and  cleaning  of  the  space  under  the  floor.  The 
stable-loft  must  also  be  aired  in  summer-time. 

Another  good  way  to  fight  the  bacterial  growth  gener- 
ally so  luxuriant  in  stables  is  to  wash  all  woodwork  with 
warm  coal-tar  in  the  spring  after  the  cleaning  and  airing. 
If  the  floor  in  the  stable  is  made  of  bowlders  (which  in 
general  must  be  considered  unsuitable,  however),  all  filthi- 
ness  between  the  stones  must  be  carefully  removed,  the 
interstices  thoroughly  soaked  with  a  solution  of  chloride 
of  lime  (one  pound  to  six  quarts  of  water),  and  the  floor 
leveled  with  new  sand.  If  the  stable  is  supplied  with 
earthen  floor  (which,  also,  for  many  reasons  cannot  be  rec- 
ommended), five  to  six  inches  of  the  upper  layer  ought  to 
be  carted  off,  the  underlying  dirt  wet  with  the  chloride-of- 
lime  solution  mentioned,  and  new  dirt  filled  in. 

If  this  disinfection  is  made  during  the  spring,  all  kinds 
of  carbolic-acid  preparations  may  be  used  instead  of  the 
chloride  of  lime;  but  disinfection  with  carbolic  acid  must 


78  MODERN   DAIRY    PRACTICE. 

not  be  made  later  during  the  summer,  since  it  will  take  a 
long  time  before  the  strong  carbolic-acid  smell  is  gone, 
and  as  the  milk  very  quickly  will  take  up  all  kinds  of 
odors  and  be  tainted  by  it.  A  suitable  carbolic-acid  solu- 
tion may  be  obtained  by  dissolving  soda  in  water  and  milk 
of  lime,  adding  some  crude  carbolic  acid  to  the  solution. 
This  mixture  has  proved  effective  in  disinfections  after  all 
kinds  of  epidemic  diseases. 

In  my  opinion  the  safest  method  is  to  disinfect  the 
stable,  even  when  infectious  diseases  have  not  appeared 
there.  This  method  will  doubtless  tend  to  increase  the 
keeping  quality  of  the  milk  and  its  products.  In  this  con- 
nection I  will  mention  that  the  milk  epidemic  at  the 
Duelund  estate  in  Denmark  (see  page  20)  did  not  dis- 
appear until  after  a  thorough  disinfection  of  both  stable 
and  dairy. 

In  the  January  number  of  the  Annales  de  VInstitut 
Pasteur,  1891,  appearing  after  the  above  chapter  was 
written,  Prof.  Duclaux  gives  a  full  account  of  some  experi- 
ments which  confirm  the  main  principles  for  the  treatment 
of  milk  laid  down  in  the  preceding  pages. 

"  It  seems  to  me,"  Duclaux  says,*  "  that  instead  of 
going  farther  in  this  direction  [sterilization  of  the  milk  by 
heat],  it  would  be  well  to  turn  around  and  ask  if  it  were 
not  better  to  avoid  that  the  heating  become  necessary,  i.e., 
prevent  all  injurious  bacteria  from  entering  into  the  milk. 
In  an  address  which  I  made  during  the  World's  Fair,  on 
June  7,  in  Trocadero  Hall,  I  said  that  milk  from  a  well- 
kept  cow  stable,  milked  very  rapidly  into  a  carefully- 
cleaned  pail,  by  a  milker  who  washed  well  his  hands  and 
the  teats  of  the  cow,  does  not  sour  more  rapidly  than 

*  Loc.  tit.,  vol.  5,  p.  59, 


SOURCES   OF   INFECTION   IN   THE   STABLE.  79 

milk  drawn  without  care  and  to  which  soda  was  added 
in  order  to  hide  its  lack  of  cleanliness.  This  thought 
arose  in  me  through  the  strong  power  of  resistance 
which  I  have  noticed  in  milk  which  was  milked  with 
extra  precautions  in  my  presence.  It  was  taken  up  by 
one  of  my  hearers — Dr.  Smester* — who  applied  it  in 
Normandy.  He  is  now  sending  milk  to  Paris  which 
has  not  been  heated  or  received  any  chemical  preserv- 
atives, but  which  still  keeps  for  a  long  time,  even  in  hot 
weather.  It  seems  to  me  that  we  ought  to  improve  in 
this  direction, — at  least  when  the  question  is  of  milk  in- 
tended for  rapid  consumption, — and  that  we  ought  not  to 
try  to  multiply  and  further  perfect  the  pasteurization 
apparatus.  It  is  true  that  an  improvement  of  these  will 
bring  about  a  perfect  neatness  on  the  farms  and  among  the 
farmers,  and  that  an  industrial  tool  is  created  sooner  than 
traditional  habits  are  changed.  But  a  change  would  soon 
occur  among  the  producers,  if  only  the  consumers  demand 
the  same.  When  the  latter  really  want  clean  milk  they 
will  get  it.  As  matters  now  stand  it  is  always  safest  to 
boil  the  milk  before  using,  if  the  consumer  is  not  fully 
certain  of  the  cleanliness  and  general  health  of  the  animals 
producing  it;  but  the  question  of  the  keeping  quality  of 
the  milk  will  nevertheless  have  taken  a  great  step  toward 
its  solution  when  it  is  correctly  understood  on  farms  and 
in  dairies  what  cleanliness  really  means." 

*  Dr.    Smester  is  continuing  his  experiments  with  a  view  of 
applying  them  on  a  large  scale. 


CHAPTER  III. 

THE  COMMON  FORMS   OF  BACTERIA  FOUND  IN 
COWS'  MILK. 

THE  milk  when  drawn  from  a  healthy  udder  being 
sterile  (see  p.  23),  the  kinds  of  micro-organisms  found  in 
the  same  are  dependent  on  the  forms  of  bacteria  found  in 
its  surroundings.  For  this  reason  we  generally  find  differ- 
ent kinds  of  bacteria  in  different  places,  and  can  often  form 
an  opinion  concerning  the  company  it  has  kept  from  a 
mere  microscopic  examination  of  the  milk.  I  shall  here 
only  recall  a  couple  of  instances  described  in  the  preceding. 
The  presence  of  bacillus  sultilis  in  the  milk  shows  plainly 
that  in  some  way  or  other  it  has  been  exposed  to  fodder 
dust,  etc.,  while  the  presence  of  peptonizing,  putrefactive 
bacteria  in  large  numbers  indicates  that  the  milk  has  been 
in  too  intimate  contact  with  manure  particles  and  other 
filthiness.  Still  more  certain  pointers  as  regards  the  causes 
of  the  infection  of  the  milk,  are  obtained  by  microscopic 
examinations  of  the  non-bacterial  impurities,  as  described 
in  the  preceding  chapter  (see  p.  31). 

Different  forms  of  bacteria  are  usually  found  in  the 
milk  during  the  different  seasons,  for  the  reason  that  the 
surroundings  of  the  milk  during  its  production  and  hand- 
ling are  not  the  same  during  different  periods  of  the  year. 
As  is  natural,  the  greatest  differences  are  found  between 
samples  of  milk  taken  when  the  cows  were  kept  in  the 

80 


BACTERIA   COMMONLY   FOUND   IN   COWS5   MILK.          81 

barn  and  when  they  were  on  pasture.  According  to  my 
observations,  these  two  kinds  of  milk  differ  from  one  an- 
other not  only  in  the  fact  that  the  milk  produced  while  on 
pasture  contains  a  much  smaller  number  of  bacteria,  but 
also  because  the  organisms  found  in  it  are  by  no  means  as 
dangerous  for  the  keeping  quality  of  the  milk  as  those  in- 
fecting the  milk  originating  in  the  stable.  This  is  espe- 
cially striking  if  the  pasture  milk  is  compared  with  milk 
from  a  dark  and  dirty  cow-stable  where  the  cows  are  stand- 
ing on  manure. 

In  view  of  the  conditions  mentioned,  we  cannot  here 
enumerate  all  or  even  the  most  common  micro-organisms 
found  in  the  milk.*  We  shall  only  consider  the  varieties 
which,  according  to  my  investigations,  are  the  most  dan- 
gerous enemies  to  the  keeping  qualities  of  our  milk.  There 
may,  of  course,  be  a  large  number  of  other  bacteria  which 
in  certain  regions,  where  I  have  not  had  an  opportunity  to 
examine  the  milk,  play  a  still  more  injurious  part  than 
those  here  mentioned. 

My  investigational  material  has  come  mainly  from 
middle  Savolak,  or  from  the  regions  around  Helsingfors 
and  Tammerfors.  A  large  number  of  samples  examined, 

*  For  a  detailed  enumeration  of  the  different  forms  of  bacteria 
found  in  cows'  milk,  see  Kramer,  "  Bakteriologie  d.  Landwirtscliaf t, " 
1892  ;  Freudenreich,  "Bakteriologie  der  Milchwirtschaft,"  1893,  pp. 
36-53;  Conn,  "The  Fermentations  of  Milk,"  1893,  pp.  17-63;  Ada- 
metz,  "  Normal  and  Abnormal  Bacteria  in  Milk,"  Oest.  Monatschr.  f. 
ThierTieilkunde,  15,  pp.  1-36  ;  Centralbl.f.  Bact.,  8,  109  ;  Schuppan, 
"Bacterien  in  Bezieh.  z.  Milchwirtschaft,"  Centralbl.  f.  Bact.,  13, 
527;  LSffler,  "Ueber  Bacterien  in  d.  Milch.,"  Berl.  klin.  Wochen- 
schr.  1887 ;  Hueppe,  "  Untersuch.  ueber  die  Zersetzungen  d.  Milch 
durch  Mikro-organismen,"  Mitt.  Kais.  Ges.  Amies,  2,  309. — W. 


o2  MODERN    DAIRY   PRACTICE. 

especially  of  sour  milk,  buttermilk,  and  sour  cream,  came 
from  different  regions  of  our  country, 
Samples  of  sweet  milk  have  generally  been 
examined  at  once  after  they  came  into  my 
possession. 

Other  samples,  taken  on  travels  in  the 
different  districts,  were  usually  not  examined 
at  once,  no  facilities  being  available.  These 
samples  were  kept  in  thin,  short,  previously 
sterilized  glass  tubes,  drawn  out  to  fine 
points  in  both  ends,  and  at  once  melted  to- 
gether. The  illustration  (Fig.  23)  shows 
such  a  tube  in  natural  size.  In  using  it 
the  outer  wall  of  the  tube  which  is  introduced 
in  the  milk  is  sterilized  over  an  alcohol  flame, 
the  points  are  broken  off  rapidly  with  a  pair 
of  recently  ignited  nippers,  the  milk  is  sucked 
in,  and  the  ends  again  melted  together.  A 
careful  record  was  kept  of  the  outward  ap- 
pearance, color,  taste,  and  odor  of  each  sample 
of  milk,  and  of  conditions  in  the  dairy  and 
barn  on  the  farms  where  the  milk  was  pro- 
duced. In  cases  where  samples  of  tuberculgus 
and  other  contagious  or  abnormal  milk  were 
taken  I  used  a  sterilized  glass  tube  of  a  some- 
what different  shape  than  the  one  just  de- 
scribed, since  it  was  undesirable  in  such 
cases  to  get  any  of  the  milk  into  the  mouth 
in  filling  it.  The  latter  kind  of  sampling 
tubes  are  of  about  double  length,  and  supplied 
FIGS.  23,  24.  with  two  reservoirs  for  the  milk,  of  which  the 

one  only  served  as  a  safety  bulb  in  sampling  (Fig.  24). 


BACTERIA   COMMONLY   FOUND   IN   COWS*   MILK.          83 

The  examination  of  the  samples  taken  and  kept  in 
this  way  cannot  of  course  give  any  information  of  the 
number  of  bacteria  in  the  original  fluid,  as  quantitative 
bacteriological  analyses,  as  shown  in  the  Introduction,  must 
be  made  immediately  after  the  sampling.  The  method 
used  will,  however,  throw  a  clear  light  on  the  question 
of  the  varieties  of  bacteria  found  in  the  different  samples. 
It  is  possible  that  some  kinds  of  bacteria  may  become  less 
active,  or  even  succumb,  if  the  sample  is  kept  too  long; 
but  all  control  analyses  which  I  have  made  have  failed  to 
show  any  appreciable  decrease  in  the  number  of  the  living 
kinds  of  bacteria,  even  after  a  lapse  of  three  months.  A 
long  confinement  in  the  glass  tube  appears,  on  the  other 
hand,  to  cause  the  destruction  of  some  forms  of  bacteria, 
while  lactic-acid  bacteria  have  shown  strong  ability  to 
multiply  even  after  having  been  kept  for  fourteen  months 
in  the  manner  described;  their  ability  to  develop  lactic- 
acid  fermentation  in  milk  was,  however,  considerably 
weakened. 

Number  of  Bacteria  in  Milk. — The  number  of  bacteria 
in  cows'  milk  depends  of  course  on  the  treatment  to 
which  the  milk  has  been  subjected  since  drawn  from 
the  udder.  This  explains  the  different  data  given  in  the 
literature  on  the  subject.  Cnopf  in  Munich  counted  the 
number  of  bacteria  in  recently  drawn  milk.  He  found  no 
less  than  60,000  to  100,000  bacteria  in  one  cubic  centimeter. 
Freudenreich  in  Eiitti,  Switzerland,  on  the  other  hand, 
found  only  9300  per  cc.  in  milk  on  its  arrival  in  the  labora- 
tory. Jensen  in  Copenhagen  says  he  is  inclined  to  think 
that  the  number  of  bacteria  in  the  milk  cans  immediately 
after  all  the  cows  have  been  milked  is  many  times  larger 
under  ordinary  Danish  conditions  than  given  by  Cnopf. 


84  MODERN   DAIKY   PBACTICE. 

The  results  found  by  me  in  case  of  different  samples  of 
milk  have  also  varied  greatly,  according  to  the  age  of  the 
sample  when  the  bacterial  content  is  determined,  as  well  as 
the  origin  of  the  milk  analyzed. 

Samples  taken  in  a  pasture  on  a  fresh,  somewhat  damp 
summer  morning  showed  the  following  average  results  as 
regards  their  bacterial  content  : 


Number  of  bacteria  in 


n  )  irk  -,KQn 

i  .  ,.  >•  10  oo  1530 

one  cubic  centimeter,  $ 

The  numbers  in  this  table  are  surprisingly  small  as  com- 
pared with  those  previously  given,  but  the  samples  were 
taken  under  particularly  favorable  conditions.  The  milk- 
ing took  place  away  from  any  dwelling-house,  in  a  pasture 
surrounded  by  woods,  during  complete  calm,  and  the  cows 
were  still  damp  after  the  moisture  and  the  fog  of  the  night 
air.  The  infection  under  these  conditions  would  naturally 
be  very  small.  During  the  two  hours  given  in  the  table 
the  milk  stood  in  the  hauling  can  in  the  pasture  and  during 
the  transportation  to  the  dairy. 

Entirely  different  data  are  obtained  in  examining  milk 
produced  in  a  barn.  The  infection  is  there  very  pro- 
nounced, even  within  the  first  half-hour  after  the  milking 
is  done. 

In  making  some  quantitative  bacteriological  analyses 
of  the  milk  produced  on  a  certain  farm  I  obtained  samples 
of  milk  from  a  stable  where  only  the  heavy  milkers  had  yet 
been  taken  in  from  the  summer  pasture.  The  stable  was 
therefore  not  filled  with  cows,  and  ordinary  winter  condi- 
tions had  not  yet  appeared  there.  This  explains  why  this 
milk  also  contained  comparatively  few  bacteria, 


BACTERIA  COMMONLY  FOUND  IN  COWS*  MILK.          85 


The  milk  was  kept  in  the  hauling-can  in  the  stable  dur- 
ing the  1J  hours  after  the  milking.  The  mouth  of  the 
can  was  covered  by  a  clean,  thin  linen  cloth  thrown  loosely 
over  it,  which  did  not  exclude  the  air,  but  to  a  large  extent 
prevented  possible  new  infection  from  bacteria  in  the  air.* 

It  was  found  in  these  experiments  that  immediately 
after  the  milking  a  very  varying  number  of  bacteria  was 
found  in  the  different  layers  of  the  rnilk.  I  was  of  the 
opinion  that  since  the  milk  in  the  pail  is  under  constant 

*  Sedgwick  and  Batchelder  (Boston  Ned.  and  Surg.  Journal,  Jan. 
14,  1892)  in  studying  the  Boston  milk  supply  made  the  following 
experiments  :  "  Milk  was  drawn  from  a  clean  and  well-kept  Hoi- 
stein  cow  in  an  unusually  decent  stable.  The  normal  milk  of  this 
cow  had  already  been  repeatedly  proved  to  be  sterile.  Milk  drawn 
by  hand  from  this  cow  with  great  care  into  sterilized  bottles,  and 
planted  quickly,  yielded  as  an  average  of  several  trials  530  bacteria 
per  cubic  centimeter.  When,  however,  the  milkman  used  the  ordi- 
nary milk-pail  of  flaring  form,  seated  himself  with  more  or  less  dis- 
turbance of  the  bedding,  and  vigorously  shook  the  udder  over  the 
pail  during  the  usual  process  of  milking,  we  found  that  the  numbers 
were  very  much  higher,  namely,  an  average  of  30,500  per  cubic 
centimeter  at  the  end  of  the  milking.  When  such  milk  is  found 
upon  the  tables  of  country  families  a  few  hours  later  it  naturally 
shows  still  more  bacteria,  doubtless  because  those  with  which  it  was 
seeded  have  had  time  to  multiply,  The  average  of  fifteen  such  sam- 
ples from  the  tables  of  families  in  Jamaica  Plain,  Cambridge,  and 
Auburndale  was  69,143  per  cubic  centimeter.  In  these  cases, 
moreover,  the  conditions  of  the  cows  and  of  the  stables  were  excep- 
tionally good,  while  the  milkmen  were  much  more  than  ordinarily 
clean  and  careful."  —  W. 


86  MODERX   DAIRY    PRACTICE. 

stirring  during  the  milking  that  the  bacterial  content 
would  be  about  even  in  the  whole  of  the  can.  But  control 
experiments  showed  in  a  very  striking  manner  that  the 
number  of  bacteria  was  largest  on  the  surface  of  the  milk. 
All  samples  taken  from  the  depth  of  the  mess  of  milk,  by 
means  of  sterilized,  so-called  Pasteur  pipettes  showed 
very  few  bacteria, — on  an  average  20.3  per  cc., — while  all 
samples  taken  from  the  surface  contained  over  200  per 
cc.  If  I  should  venture  an  explanation  of  this  phenomenon, 
I  would  say  that  it  still  more  confirms  the  observations 
made  in  the  preceding,  that  one  of  the  main  sources  of  the 
infection  of  the  milk  is  the  lower  part  of  the  stomach  and 
the  udder  region  of  the  cow,  from  which  filthiness  with  ac- 
companying bacteria  all  the  time  is  falling  down  during 
the  milking. 

Milk  from  stables  where  winter  conditions  have  entered 
has  usually  shown  a  higher  bacteria  content.  Bacteriologi- 
cal analyses  of  such  milk  half  an  hour  after  the  close  of 
the  milking  have  given  the  following  data  for  the  content 
per  cubic  centimeter:  4100;  2450;  1890;  14,670;  830; 
3030;  5450;  21,700;  and  1030. 

I  have  made  bacteriological  analyses  of  several  samples 
of  milk  supplied  to  creameries,  the  samples  being  taken 
under  different  conditions.  The  results  naturally  differed 
greatly.  Milk  from  a  well-conducted  farm  was  examined 
after  standing  for  one  hour  in  the  warm  stable  and  then 
hauled  to  the  creamery  near  by.  The  milk  contained  on 
an  average  4500  bacteria  per  cubic  centimeter.  Milk 
from  a  filthy  stable  where  the  cows  were  standing  in 
manure,  on  a  warm  day,  transported  by  rail  to  the  city 
where  I  took  the  sample,  seven  hours  after  the  milking,  con- 
tained 25,000  bacteria  per  cc.  After  having  been  kept 


BACTERIA  COMMONLY   FOUND   IN   COWS*  MILK.          87 

for  an  hour  in  the  rather  warm  laboratory  the  sample  was 
found  to  contain  considerably  over  100,000  organisms  per 
cubic  centimeter.  From  a  filthy  and  dark  cow  stable, 
spoken  of  more  in  detail  in  Chapter  V,  a  sample  of  milk 
came  which  three-fourths  of  an  hour  after  milking  showed 
not  less  than  about  670,000  bacteria  per  cc.  The  bac- 
terial content  of  three  samples  of  milk  taken  on  three 
consecutive  days  from  this  stable,  did  not  vary  much, 
the  analyses  showing  the  following  average  figures  per 
cc. :  730,000,  560,000,  and  780,000.  The  most  infected  milk 
ever  analyzed  by  me  was  from  a  milk  store  in  Wiesbaden 
(Germany).  Its  age  and  the  treatment  to  which  it  had 
been  subjected  could  not  be  ascertained.  It  was  sold  as 
fresh  new  milk,  did  not  taste  sour,  but  had  a  decided  "  off  " 
flavor;  on  analysis  it  was  found  to  contain  an  immense 
number  of  bacteria,  according  to  a  low  estimate  several 
tens  of  millions  per  cubic  centimeter.  Any  exact  figures 
in  this  analysis  could  not  be  obtained  by  the  methods  then 
at  my  disposal.* 

*  The  influence  of  the  season  on  the  bacterial  content  of  milk  is 
illustrated  by  the  data  furnished  by  Dr.  Russell  as  given  on  p.  92, 
foot-note. 

The  weather  doubtless  also  greatly  influences  the  number  of  bac- 
teria found  in  milk.  Dr.  Russell  has  kindly  furnished  me  with  the 
following  illustration  :  The  milk  of  one  of  the  patrons  at  the  Wis- 
consin University  Creamery  was  examined  in  May  1894,  on  two 
succeeding  days,  the  sampling  being  done  at  the  same  time  both  days; 
it  contained  1,150,000  and  48,000  bacteria  per  cubic  centimeter,  on 
an  average,  during  the  two  days.  The  first  day  was  very  warm, 
while  the  second  was  cold  and  rainy. 

The  milk  contained  seven  to  ten  different  species  of  bacteria ;  slimy 
organisms  were  isolated  in  large  numbers  ;  hay  bacillus  was  quite 
numerous,  and  pitted  liquefiers  very  numerous  in  the  sample. — W. 


88  MODERN   DAIRY   PRACTICE. 

Increase  in  Bacterial  Content  of  Milk. — The  increase 
of  the  bacteria  in  milk  depends  of  course  both  on  the  tem- 
perature and  on  the  kinds  appearing  in  the  milk.  The 
influence  of  the  former  factor  is  shown  by  the  following 
investigations : 

Cnopf  and  Escherich  in  Munich  found  60,000-100,000 
bacteria  per  cc.  in  a  sample  of  milk  recently  drawn  under 
precautions  of  great  cleanliness.  This  milk  was  kept  in  a 
cool  cellar  at  a  temperature  of  12°.5  C.  (56°.5  F.).  After 
two  hours  the  number  of  bacteria  was  4  times  larger  than 
at  the  beginning,  after  four  hours  8  times  larger,  after  five 
hours  26  times  larger,  and  after  six  hours  435  times  larger. 
[Another  portion  of  the  same  milk  was  kept  at  35°  C.  in 
an  incubator;  the  bacteria  contained  in  it  had  multiplied 

23  times  after  two  hours  and  215  times  after  four  hours, 
1830  times  after  five  hours  and  3800  times  after  six  hours. 
The  development  of  bacteria  in  milk  kept  on  ice  was  so 
small  during  this  time  that  it  could  hardly  be  ascertained, 
but  in  the  course  of  some  days  it  reached  as  high  figures  as 
in  the  other  samples.* — W.] 

From  the  laboratory  at  Riitti  the  following  table  is  fur- 
nished concerning  the  number  of  bacteria  per  cc.  in 
milk  of  Nov.  14, 1889.  On  the  arrival  at  the  laboratory 
there  was  found  9300  bacteria  per  cc.  in  the  milk. 

INCREASE  IN  BACTERIAL  CONTENT. 

When  kept  at       When  kept  at    When  kept 
15°  C.  25°  C.  at  35°  C. 

3  hours  later 1.06  times           2  times            4  times 

6  hours  later 2.5      "              18.5  "  1,290    " 

9  hours  later 5.0      «            107.5   «  3,794    " 

24  hours  later....  163        «  62,097.     «  5,376    « 

*  Centra®.  /.  Bakteriologie,  6,  554. 


BACTERIA   COMMONLY   FOUND   IK   COWS*   MILK.          89 

The  following  instructive  facts  are  shown  from  these 
figures:*  1.  At  15°  0.  (59°  F.)  there  was  no  increase  dur- 
ing the  first  three  hours,  and  during  the  first  six  hours  only 
an  insignificant  one.  2.  At  25°  C.  (77°  F.)  the  increase  was 
insignificant  during  the  first  three  hours,  but  the  number 
of  bacteria  then  increased  rapidly  at  the  temperature 
so  favorable  to  the  growth  of  the  bacteria.  3.  At  35°  0. 
(95°  F.)  the  development  was  rather  rapid  from  the  start, 
but  the  increase  in  the  bacterial  content  was  still  after 
twenty-four  hours  not  so  large  as  at  the  last-mentioned 
lower  and  evidently  more  favorable  temperature. 

If  a  still  lower  temperature  than  59°  F.  (15°  0.)  be  used 
for  keeping  the  milk  the  bacterial  growth  is  nearly  com- 
pletely checked.  If  the  temperature  of  the  milk  is  low- 
ered to  45°  F.  (7°  C.)  immediately  after  the  milking,  the 
bacterial  content  according  to  my  results  is  practically 
unchanged  after  twenty-four  hours,  and  even  after  a  still 
longer  time  from  what  it  was  at  the  beginning  of  the  cooling. 
I  have,  however,  observed  in  isolated  cases  that  even  at  this 
temperature  a  considerable  increase  has  taken  place ;  this 
increase  always  stopped  entirely  when  the  bacteria  were 
subjected  to  this  temperature  for  5-6  hours.  The  bacteria 
able  to  multiply  even  at  45°  F.  (7°  C.)  thus  appear  to  be 
slowly  paralyzed  under  the  influence  of  this  temperature. 
Even  when  the  milk  has  had  a  temperature  of  43°  F. 
(6°  0.),  an  increase  of  the  bacteria  has  twice  been  found: 
in  the  one  instance  the  increase,  strange  to  say,  took 
place  a  long  time  after  the  temperature  of  the  milk  had 
been  lowered  to  this  point.  The  tenacious  organisms 

*  See  also  results  obtained  by  Miquel,  Ann.  Microgr.  1889,  Dec. 
No. ;  and  by  Baumann  (Inaug.  Dissert.  Univ.  KSnigsberg,  1893,  pp. 
16,17).— W. 


90  MODERN   DAIRY   PRACTICE. 

which  thrived  so  well  at  this  low  temperature  were  not, 
however,  of  a  kind  that  would  exert  any  influence  on  the 
quality  of  the  milk.  With  the  temperature  of  the  milk  at 
39°  F.  (4°  0.)  I  have  never,  no  matter  how  long  it  was 
kept,  been  able  to  observe  any  increase  in  the  bacteria  con- 
tent; this  has  always  remained  unchanged  from  the  mo- 
ment the  temperature  sank  to  39°  F.  (4°  C.). 

It  may  finally  be  mentioned  that  Cnopf  *  analyzed  milk 
samples  which  contained  from  200,000  to  6,000,000  bac- 
teria per  cubic  centimeter  5-6  hours  after  the  milking 
(average  over  1,000,000  per  cc.).f 

*  Centrafol.  f.  Bact.  6,553. 

f  The  determinations  of  the  bacterial  content  of  market  milk  or 
of  milk  peddled  in  cities  have  as  a  rule  given  exceedingly  high  fig- 
ures, owing  to  the  comparatively  long  interval  between  the  milking 
and  the  sampling.  The  following  results  have  been  obtained  in  the 
main  investigations  in  this  line  : 

Clauss  (Inaug.  Dissert.  Wiirzberg,  1890  ;  Cliem.  Centralbl.  1890, 
518)  found  from  222,000  to  2.3  million  bacteria  per  cubic  centimeter 
in  eight  samples  of  Wlirzburg  market  milk  taken  during  winter 
time  ;  average  1-2  million  per  cc. 

Hohenkamp  (Arch.  f.  Hyg.,  14,  260)  found  from  1.9  to  7.2  mil- 
lions in  the  market  milk  of  the  same  city  during  the  summer. 

Buiwid  (vide  Knochenstiern)  in  1890  found  on  an  average  4  mil- 
lion germs  in  sixteen  samples  of  Warsaw  milk. 

Freudenreich  (vide  Knochenstiern)  found  10, 000  to  20,000  bacteria 
per  cc.  of  Riitti  milk. 

Geuns  (Arch.  f.  Hyg.,  3, 479)  found  fresh  milk  sold  in  Amsterdam 
to  contain  2.5  millions,  and  when  ten  hours  old  10.5  millions. 

Cunningham  (Arch.  f.  Hyg.,  12)  found  3400  to  300,000  bacteria 
per  cc.  of  Calcutta  milk  taken  during  summer  1891. 

Renk  (Centralbl.  f.  Bact.,  10,  193)  found  6-30.7  million  per  cc.  in 
Halle  milk. 

Uhl  (Zeitschr.f.  Hyg.,  12,  475)  found  from  83,100  to  170  millions 
av.  22.9  millions,  in  thirty  samples  of  Giessen  market  milk,  taken 


BACTERIA  COMMONLY  FOUND  IN  COWS*  MILK.         91 

Comparing  the  data  just  given  concerning  the  number 
of  bacteria  found  in  milk,  it  will  be  seen  that  milk  under 
certain  conditions  may  contain  very  few  bacteria  and 
under  other  conditions  immense  numbers  of  these  organ- 
isms. That  the  latter  is  always  the  case  with  milk  com- 
ing from  filthy  stables  is  apparent  from  the  data  given, 
and  it  is  equally  apparent  that  cleanliness  and  neatness  in 
the  handling  of  the  milk  may  cause  a  considerable  decrease 
in  its  bacterial  content.* 

during  May  1892,  and  from  10,500  to  13.6  millions,  av.  2.9  millions, 
in  the  same  kind  of  milk  sampled  during  June  1892. 

Knochenstiern  (Inaug.  Dissert.  Univ.  Dorpat,  1893)  obtained  the 
following  results  in  his  investigations  of  the  Dorpat  milk  supply  : 
40  samples  of  milk  sold  by  milkmen  : 

36,000-83   millions;  av.  10.2  millions 
25  samples  of  milk  from  village  dairies : 

90,000-103         "       "    12 
35  samples  of  milk  sold  on  market-place  : 

137,000-287          "       "25         " 
40  samples  of  milk  sold  in  milk  stores : 

11,600-257         "       "    30 

Gernhardt  (Inaug.  Dissert.  Univ.  Jurjew,  1893)  found  similar  re- 
sults for  Dorpat  milk. 

See  also  Baumann  (Inaug.  Dissert.  Univ.  Konigsberg,  1893,  pp. 
16,  17).— W. 

*  The  number  of  bacteria  in  American  milk  has  been  studied  by 
but  few  investigators.  Sedgwick  and  Batchelder  examined  the  milk 
supply  of  Boston  bacteriologically  (Boston  Med.  and  Surg.  Jour., 
1892,  Jan.  14)  ;  the  average  number  of  bacteria  found  in  fifty-seven 
samples  in  the  spring  of  1890  was  2,355,500  per  cubic  centimeter. 
Sixteen  samples  obtained  from  groceries  contained  4,577,000  per  cc. 
Ten  samples  collected  from  "well-to-do  families  upon  the  Back 
Bay"  showed  an  average  of  1,438,000  per  cc.  The  lowest  number 
found  in  Boston  milk  supplied  in  the  ordinary  way  was  30,600  per  cc. 

Dr.  Russell  (private  communication)  determined  the  bacteria  con- 
tent of  morning  milk  as  delivered  to  customers  in  Madison,  Wis. : 


92  MODERN   DAIRY   PRACTICE. 

Kinds,  not  Numbers,  of  Bacteria  of  Most  Importance. 
— It  must  be  remembered,  however,  that  in  the  infection 
of  milk  with  bacteria,  as  in  every  other  infection,  the  main 
importance  does  not  lie  in  the  large  or  small  number  of 
bacteria,  but  in  their  qualities  and  nature.  It  is  a  com- 
mon observation  that  a  large  number  of  different  kinds  of 
bacteria  are  found  in  the  milk  by  the  first  examination  in 
the  stable,  but  in  later  examinations  of  the  same  milk 
the  number  of  different  kinds  will  be  found  considerably 
reduced.  The  struggle  for  existence  thus  seems  to  be  as 
pronounced  in  the  microscopic  as  in  the  macroscopic 
world.  The  milk  is  infected  from  different  sources  by 
different  kinds  of  bacteria,  and  each  of  them  begins  to 
hunt  for  sustenance  in  the  new  nutritive  medium,  and 
seeks  to  gain  superiority  over  the  others.  The  struggle  is 
for  life  and  for  the  greatest  power,  for  even  among  these 
pygmies  of  the  living  world  the  old  maxim  holds  good, 
that  he  who  has  the  power  appropriates  for  himself  all  the 
good  things  of  life.  The  organisms,  for  one  reason  or 
another  gaining  the  upper  hand,  increase  so  rapidly  that  the 
others  at  best  can  only  just  save  their  lives,  and  are  unable 
to  exert  their  vital  functions  on  a  large  scale.  They  remain 
helplessly  in  the  minority  as  long  as  the  conditions  are  favor- 
able for  their  more  favored  conquerors.  We  thus  find  that 
only  a  few  forms  of  bacteria  have  been  able  to  increase  in 
preponderating  numbers  in  samples  of  milk  that  have  been 

from  35,000  to  275,000  was  found  per  cc.  on  an  average  during  April 
(1894),  and  from  380,000  to  2,000,000  per  cc.  during  May  and  June 
See  also  foot-note  on  p.  87. 

Pammel  (Iowa  Experiment  Station  Bulletin  No.  21,  p.  801)  found 
571,900  bacteria  in  milk  "  just  before  the  curd  was  ready  to  cut  for 
cheese"  ;  another  sample  contained  165,000  bacteria  per  cc. — W. 


BACTERIA   COMMONLY   FOUND   IN    COWS*   MILK.          93 

kept  for  about  one  day.  Among  the  determining  causes 
for  the  superiority  of  these  few  forms  three  circumstances 
may  especially  be  pointed  out : 

1.  The  milk  is  a  better  nutritive  medium  for  these 
organisms  than  for  their  competitors.     Although  milk  in 
general  may  be  considered  an  excellent  growing  place  for 
bacteria,  certain  kinds  seem  to  be  especially  adapted  to 
development  in  this  substratum. 

2.  The  temperature  present  is  more  favorable  for  the 
conquering  kinds  than  for  the  others.     Experience  shows 
that  a  difference  in  temperature  of  2°-4°  F.  may  have  a 
decided  influence  on  the  development  of  bacteria,  a  fact 
which  is  apparent  in  a  striking  manner  in  the  manufac- 
ture of  the  different  kinds  of  cheese. 

3.  If  the  milk  has  become  largely  infected  with  a  cer- 
tain kind  of  bacteria,  this  is  very  apt  to  keep  the  superior- 
ity, even  if  the   milk  generally  speaking  is  not  a  very 
good  nutritive  medium  for  it.     Such  "  mass-infections " 
of  a  certain  bacteria  frequently  occur  in  the  handling  of 
the  milk  on  the  farm.     Accidents  seem  to  play  an  impor- 
tant part  in  this  matter.     In  several  cow  stables  it  seems 
to  be  the  rule  that  such  mass-infection  takes  place.     This 
was,  e.g.,  the  case  in  a  stable  where,  as  mentioned  in  the 
preceding  chapter  (see  p.  53),  unclean  straw   and  rusty 
chaff  were  used  day  after  day. 

Fortunately,  however,  it  is  always  not  the  case  that  Jhe 
conquering  species  are  injurious  to  the  quality  of  the  milk. 
I  have  seen  examples  where  milk  which  was  normal  both  to 
taste  and  smell,  as  well  as  to  consistency  in  general,  con- 
tained an  immense  number  of  bacteria  which  did  not  then 
interfere  with  the  quality  of  the  milk.  Among  the  species 
found  in  such  milk  I  have  observed  bacteria,  which  later  on 


94  MODERN   DAIRY    PRACTICE. 

exerted  a  more  or  less  injurious  influence  on  the  butter 
or  the  cheese  made  from  the  milk. 

Some  bacteria  may  furthermore  appear  in  the  milk 
which  do  not  in  themselves  have  the  power  to  change 
appreciably  its  quality,  but  which  prepare  favorable  con- 
ditions for  other,  injurious  bacteria.  As  a  transition 
group  between  these  organisms  and  those  directly  de- 
structive of  the  milk,  some  species  may  be  included  that 
are  able  both  to  change  the  quality  of  the  milk  to  a 
considerable  extent  and  to  prepare  a  good  field  for  other 
bacteria,  which  in  their  turn  produce  other  kinds  of  fer- 
mentations. 

CLASSIFICATION    OF    BACTERIA    FOUND   IN    MILK. 

In  trying  to  classify  the  common  forms  of  bacteria 
found  in  milk,  I  have  separated  them  into  the  following 
four  groups: 

I.  Indifferent  bacteria. 

II.  Bacteria  indifferent  in  milk,  but  active  in  the  milk 
products. 

III.  Indirectly  injurious  bacteria. 

IV.  Injurious  bacteria. 

I.  Indifferent  Bacteria. — The  species  belonging  to  this 
group  are  of  course  of  small  interest  in  studying  the  prob- 
lem of  the  bacteriology  of  the  dairy,  and  will  therefore  not 
be  described  in  detail  here.  In  deciding  certain  questions, 
as,  e.g.,  whether  a  certain  sample  of  milk  has  been  infected 
by  bacteria  in  the  air  or  by  such  originating  in  manure 
particles,  the  indifferent  bacterial  impurities  may  be  of 
some  importance.  They  seem,  however,  to  show  such  a 


MILK.          95 

different  appearance  in  different  localities  that  only  after 
specific  investigations  of  the  local  bacteriological  conditions 
can  there  often  be  any  question  of  applying  them  as  decid- 
ing factors. 

II.  Bacteria  Indifferent  in  Milk  but  Active  in  its  Prod- 
ucts.— The  species  belonging  to  the  second  group  which  I 
have  met  with  will  be  described  in  later  chapters.     On 
account  of  the  many  difficulties  met  with  in  the  examina- 
tion of  these  bacteria,  I  have  unfortunately  only  to  a  small 
extent  been  able  to  throw  any  light  on  their  nature  and 
qualities. 

III.  Indirectly  Injurious  Bacteria  which  Produce  Fa- 
vorable Conditions  for  Bacteria  Injurious  to  the  Milk. — 
The  third  group  includes  first  of  all  several  bacteria  caus- 
ing alkaline  reaction  in  the  milk.     These  bacteria  may 
play  also  a  certain  part  in  the  dairy  industry  of  Finland. 
On  a  farm  in  Karelen,  which  I  visited  a  couple  of  years 
ago,  I  found  the  housewife  almost  in  despair.     She  said 
that  tho  milk  had  not  soured  properly  during  the  whole 
summer,  and  as  a  result  inferior  butter  was  made  during 
this  time,  while  previously  she  had  always  prided  herself 
on  making  a  mildly  acid,  first-class  butter.     Her  supply 
of  butter  on  hand  also  showed  that  she  had  every  reason  to 
be  dissatisfied.    The  butter  was  mottled,  insipid,  and  had  a 
repugnant  taste.    During  the  early  part  of  the  summer  the 
milk  had  soured,  although  it  took  a  long  time  for  it  to 
do  so;  now  the  souring  did  not  seem  to  be  forthcoming 
at  all.     The  milk  stood  in  the  pans  for  days,  the  cream 
rose,  but  did  not  thicken.     It  did  not  taste  sour,  and 
had  no  appreciable  after-taste.     Tested  with  litmus-paper 
the  milk  showed  a  distinct   alkaline    reaction.      I   was 
not  able  to  investigate  this  interesting  material  bacterio- 


96  MODERN   DAIRY   PRACTICE. 

logically,  as  the  samples  taken  in  sterilized-glass  tubes 
were  accidentally  lost.  It  may  be  added  that  since  I  could 
not  arrange  any  disinfection  of  the  dairy  and  milk  vessels 
at  the  place,  being  far  off  in  the  wilderness,  I  had  to  advise 
her  to  seek  a  remedy  entirely  opposite  to  what  I  should 
have  advised  under  different  conditions — viz.,  to  infect  in 
every  way  possible  the  dairy,  milk-pails,  pans,  churn,  the 
cows'  udders,  etc.,  with  sour  milk  from  a  neighboring  farm, 
where  the  milk  soured  in  the  regular  way.  This  "  niass- 
infection"  had  the  desired  effect,  according  to  what  I 
learned  on  a  journey  in  the  same  region  during  last  sum- 
mer. 

A  case  of  similar  nature  was  observed  during  the  same 
summer  on  an  estate  in  Savolaks.  It  proved  impossible  to 
obtain  ordinary  sour  milk  at  this  place.  The  milk  was 
left  to  sour  in  the  usual  way  on  the  pantry-shelf,  where  it 
had  always  gone  through  the  regular  lactic  fermentation 
during  previous  summers,  and  had  formed  good  sour  milk. 
During  this  whole  summer  the  sour  milk  had  been  of  a 
rather  loose  consistency  and  mostly  of  an  insipid  taste. 
When  kept  for  some  time  it  assumed  an  obnoxious,  rotten 
taste.  The  milk  soon  showed  smaller  and  smaller  ten- 
dency to  coagulate,  while  the  bad  taste  appeared  earlier. 
The  cream  rose  rather  rapidly  to  the  surface  and  had  a 
tough  consistency  (in  this  respect  different  from  the  ex- 
ample mentioned  above),  but  the  skim-milk  was  not  viscous 
and  had  a  characteristic  greenish-blue  color.  The  milk 
did  not  keep  this  appearance  long,  however.  The  surface 
of  the  cream  turned  grayish  brown,  and  swelled  in  places 
on  account  of  gas  generation.  At  the  same  time  a  dis- 
agreeable smell  and  taste  was  noticed,  for  which  reason 
the  milk  had  to  be  removed  from  the  larder.  During 


BACTERIA   COMMONLY   FOUND   IN   COWS'   MILK.         97 

several  weeks  it  was  impossible  to  prepare  satisfactory 
sour  milk  on  this  farm,  although  the  pans  were  finally 
placed  in  another  room  and  the  vessels  were  carefully 
cleaned.  At  last  they  began  to  inoculate  the  milk  with 
ordinary  sour  buttermilk,  and  after  a  considerable  time 
succeeded  in  this  manner  in  making  common  sour  milk. 
Not  till  late  in  the  fall  did  the  milk  again  turn  sour  in 
the  ordinary  way,  without  any  separate  inoculation  being 
necessary. 

The  greenish-blue  skim-milk  in  the  first  unsuccessful 
sour  milk  gave  a  very  distinct  alkaline  reaction  and  con- 
tained a  large  number  of  bactei-ia,  among  which  a  short, 
staff-like  bacillus  was  especially  noticeable.  By  pure  cult- 
ures of  this  bacteria  it  was  learned  that  it  was  in  the  main 
similar  to  the  blue-milk  bacillus  (Bacillus  cyanogenus) 
common  in  Germany,  and  more  particularly  similar  to  the 
form  of  it  first  investigated  by  Hueppe,  and  claimed  by 
him  to  be  the  typical  and  regular  cause  of  blue  milk.  This 
has  been  studied  again  of  late  by  Scholl,  and  duly  char- 
acterized as  a  variety  (or  species)  distinctly  different  from 
the  forms  described  by  Loffler  and  others.  It  does  not 
peptonize  gelatine,  but  produces  in  the  same  a  fine  green 
coloring-matter  resembling  chlorophyll;  the  other  kinds 
of  bacteria  produce  a  brownish  coloration  in  gelatine. 
Neither  the  bacterium  isolated  by  me  nor  the  blue-milk 
bacteria  found  in  Germany  caused  coagulation  or  fermen- 
tation of  acid  when  inoculated  in  sterile  milk;  it  was  some- 
times observed  that  the  milk  was  for  a  while  viscous  and 
thick-flowing.  This,  however,  seemed  soon  to  disappear. 
The  milk  turned  alkaline  if  it  previously  was  weakly  acid 
or  neutral.  I  have  been  unable  to  observe  any  blue  colora- 
tion of  the  surface  of  the  milk;  the  lower  layers  of  the 


98  MODERN    DAIRY    PRACTICE. 

milk  seemed,  however,  to  assume  a  greenish-blue  colora- 
tion. 

Small  micrococci  appeared  in  the  same  milk,  and  these 
also  produced  a  distinct  alkaline  reaction  in  it.  The  cult- 
ures in  milk  of  this  bacterium  had  a  disagreeable  odor, 
resembling  that  of  ammonia.  A  mold,  Oidium  lactis,  was 
also  observed  in  large  numbers  in  the  milk.  This  is  another 
micro-organism  which  produces  alkaline  reaction  in  the 
milk.  The  three  latter  organisms  were  by  far  the  more 
numerous  in  the  sample  of  milk  mentioned.  Lactic-acid 
bacteria  were  also  found,  but  they  had  been  largely  sup- 
planted. In  two  calculations  of  the  number  of  bacteria 
in  one  cubic  centimeter  the  ratio  of  lactic-acid  bacteria 
to  bacteria  producing  the  bluish-green  color  in  the  milk 
was  about  as  1 :  40,000.  Unfortunately  I  was  unable  to 
obtain  exact  data  as  to  this  ratio  by  proper  control  ex- 
periments. The  micrococcus  mentioned  was  greatly  in 
the  minority,  both  in  the  cream  and  in  the  lower  layers  of 
the  milk. 

By  an  analysis  of  this  milk  made  since  the  change  in 
the  cream -layer  spoken  of  had  occurred,  I  was  surprised  to 
find  the  relation  between  the  different  species  of  bacteria 
greatly  changed,  as  could  readily  be  seen  by  the  microscope. 
The  micrococci  had  gained  the  upper  hand  in  the  cream 
layer,  and  the  bacteria  resembling  the  blue-milk  bacillus 
had  been  forced  to  the  lower  layers  of  the  milk,  where  they 
lived  a  very  feeble  life,  as  was  proved  by  later  examinations. 
Being  aerobic  bacteria,  this  might  be  inferred.  The  lactic- 
acid  bacteria  were  in  a  very  small  minority  during  the 
whole  experiment,  both  in  the  milk  itself  and  in  the  cream 
layer.  It  is  plain  that  the  bacteria  resembling  the  blue- 
milk  bacillus  produced  favorable  conditions  for  the  micro- 


BACTERIA   COMMONLY   FOUND   IN   COWS'   MILK.         99 

cocci  which  can  only  multiply  in  a  distinctly  alkaline  sub- 
stratum. When  the  milk  once  had  this  reaction  due  to 
the  activity  of  the  bacteria  mentioned,  they  could  develop, 
which  they  did  to  such  an  extent  as  to  put  their  benefac- 
tors to  flight.  The  cream  then  obtained  the  disagreeable 
taste  and  smell  before  mentioned  as  the  last  stage  in  the 
changes  of  the  milk. 

According  to  my  experience  the  moulds  Oidium  lactis 
spoken  of,  under  which  name  several  species  seem  to  hide, 
often  makes  the  substratum  more  favorable  for  various 
bacteria — a  fact  to  which  I  have  referred  in  an  earlier  pub- 
lication.* 

To  the  third  group  (indirectly  injurious  bacteria)  some 
bacteria  causing  acidity  in  the  milk  may  also  be  referred. 
They  more  properly  belong  to  the  fourth  group,  how- 
ever, and  will  be  treated  there.  Although  the  bacteria 
in  general  require  an  alkaline  or  neutral  reaction  in 
the  substratum,  some  are  found  demanding  an  acid  reac- 
tion. These  are,  first  of  all,  the  butyric-acid  bacteria. 
They  thrive  only  in  a  strongly  acid  medium,  and  are  there- 
fore most  frequently  found  in  sour  milk,  where  they  strug- 
gle for  a  living  with  the  lactic-acid  bacteria.  These  latter 
are  thus  their  forerunners,  which  produce  a  favorable  nutri- 
tive medium  for  the  butyric-acid  bacteria,  and  are  then 
forced  out  of  the  way  by  these.  Although  the  butyric-acid 
bacteria  at  first  are  only  in  an  exceedingly  small  minority 
among  the  micro-organisms  of  the  milk,  they  multiply  rap- 
idly as  soon  as  the  substratum  grows  too  acid  for  the 
lactic-acid  bacteria,  and  begin  to  make  their  presence  felt 

*  "  Saprofyta  mikro-organismer  i  komjSlk,  I,"  Helsingfors, 
1890,  p.  80;  see  also  Lang  and  Freudenreich,  "Oidium  lactis  in 
Milk,"  Ldw.  Jahrb.  Schw.  7,  p.  229. 


100  MODERN   DAIRY   PRACTICE. 

by  starting  the  bad-smelling  butyric  fermentation  ("ran- 
cidity"). These  two  processes — the  lactic  and  butyric 
fermentation — seem  to  be  coherent  to  such  an  extent  that 
a  German  author  (Wigand)  recently  even  asserted  that  the 
butyric  fermentation  is  simply  a  continuation  of  the  lactic- 
acid  fermentation  ("  ein  weiteres  Stadium  der  Milchsaure- 
galirung  "). 

IV.  Bacteria  Injurious  to  the  Milk. — Bacteria  of  very 
different  kinds  and  of  highly- varying  characteristics  belong 
to  this  group.  In  order  more  readily  to  obtain  a  general 
view  of  them,  we  will  separate  them  into  the  following  sub- 
divisions : 

1.  Bacteria  producing  acidity  in  the  milk. 

a.  Bacteria  producing  lactic  fermentation. 
5.  Bacteria  producing  butyric  fermentation. 
c.  Bacteria  producing  volatile  acids  in  the  milk. 

2.  Bacteria  producing  no  acidity  in  the  milk. 

a.  Bacteria  causing  coagulation  of  the  casein. 

"b.  Bacteria  causing  coagulation  of  the  casein  and 

subsequent  peptonization  of  the  coagulum. 
c.  Bacteria  bringing  the  casein  into  fermentation 

without  coagulating  it. 

We  shall  below  briefly  mention  the  main  bacteria  in- 
cluded under  the  preceding  divisions. 

la.  Lactic  Fermentation. — There  are  many  kinds  of 
bacteria  producing  lactic  fermentation.  Most  of  them 
belong  to  the  bacteria  proper,  while  others  belong  to  the 
yeasts.  The  lactic-acid  bacteria  will  be  described  more 
fully  under  the  "  Ripening  of  the  Cream." 

Besides  the  lactic-acid  bacteria  proper,  a  number  of 
other  bacteria  may  be  included  under  this  division  which 
only  incidentally  produce  fermentation.  Certain  infec- 


BACTERIA  COMMONLY   FOUND   IN   COWS'   MILK.       lOl 

tious  bacteria,  as  the  Mastitis  bacterium  and  some  color- 
producing  bacteria,  as  the  Bacillus  prodigiosus,  belong  here. 
The  latter  has  not,  to  my  knowledge,  been  found  ill  our 
country.* 

1£.  Butyric  Fermentation. — The  form  of  the  many 
butyric-acid  bacteria  which  I  have  met  with  in  this  coun- 
try has  in  the  main  proved  similar  to  the  one  first  isolated 
and  described  by  Hueppe.  It  is  aerobic,  and  produces  a 
slight  coagulation  of  the  casein,  which,  however,  later  on 
is  peptonized.  It  may  therefore  also  be  referred  to  one  of 
the  following  groups.  If  sterilized  milk  be  inoculated 
with  such  butyric-acid  bacilli,  a  clear  liquid  layer  of  a  gray- 
ish color  will  be  found  after  keeping  the  cultures  for  a 
couple  of  days  at  about  86°  F.  (30°  C.).  Under  this  layer 
a  lumpy  casein  coagulum  is  found,  which  sinks  deeper 
as  the  clear  liquid  increases.  The  coagulum  gradually 
disappears,  and  after  some  time  will  be  entirely  pepton- 
ized. Milk  changed  in  this  way  has  a  very  bitter  taste. 

Ic.  Bacteria  Producing  Volatile  Acids.  —  Among  the 
bacteria  producing  volatile  acids  in  the  milk  may  be  men- 
tioned first  the  tfdwo-bacteria  forms,  which  are  rather  fre- 
quent in  milk.  They  all  appear  with  a  translucent,  sack- 
formed  cover,  in  which  the  fine,  long,  immovable  bacteria 
are  entirely  wrapped  up,  and  in  which  the  division  of  the 
bacteria  seems  to  take  place.  Some  hours  after  the  ster- 
ilized milk  has  been  inoculated  with  such  bacteria  the  sam- 
ple will  be  changed  both  in  appearance  and  consistency. 
It  assumes  a  brown  to  grayish  color  and  becomes  rather 
viscous.  No  appreciable  coagulation  will  be  found.  Grad- 
ually the  milk  will  be  changed  to  a  translucent,  grayish- 

*  The  same  is  true  in  case  of  America  (Russell).— W. 


102  MODERN  DAIRY  PRACTICE. 

colored,  somewhat  viscous  fluid,  which  would  hardly  remind 
one  of  milk.  It  is  further  characteristic  for  the  culture  of 
these  bacteria  in  milk  that  a  lively  generation  of  gas  often 
takes  place  in  the  substratum.  Carbonic  acid  seems  to  be 
the  main  gas  generated.  I  have  also  observed  a  smell 
suggesting  sulphuretted  hydrogen.  The  presence  of  small 
quantities  of  alcohol  and  acetic  acid  may  further  be  shown 
by  distillation  of  the  milk. 

Among  the  organisms  belonging  to  this  family  I  have 
only  observed  two  varieties  in  Finnish  milk — the  one  very 
thin  and  long,  the  other  thicker  and  shorter.  Neither 
seem  to  shun  daylight  particularly ;  they  are  both  killed  by 
a  single  rapid  heating  of  the  substratum  to  158°  F.  (70°  C.). 
They  seem  to  be  found  almost  regularly  in  stringy  milk;  * 
they  doubtless  play  a  part  in  the  formation  of  this  milk, 
although  they  also  seem  to  be  assisted  by  others,  e.g.,  of  a 
lactic-acid  bacterium  appearing  as  streptococcus;  the  latter 
does  not  produce  volatile  acids,  as  is  the  case  with  other 
lactic-acid  bacteria. 

Za.  Bacteria  Causing  Coagulation  of  the  Casein. — 
Three  different  varieties  found  in  Finnish  milk  are  in- 
cluded in  this  subdivision.  Of  this  number  only  one,  how- 
ever, calls  for  special  mention,  since  the  other  two  seem  to 
be  comparatively  rare.  The  third  one  is  very  common,  and 
in  my  investigations  has  been  found  to  appear  in  particu- 
larly large  numbers  in  milk  which  had  come  in  contact 
with  manure-particles,  etc.  It  is  a  short  bacillus 
(1.5  X  .5  /*),  often  thinner  in  the  middle  and  with  round- 
ed ends.  Its  power  of  locomotion  is  very  pronounced. 
Thread-formed  runners  from  the  small  colonies  are  no- 

*  See  "  Saprophytic  Micro-organisms  in  Cows'  Milk,"  p.  27. 


BACTERIA   COMMONLY   tfOUND   IN    COWS*   MILK.       103 

ticed  on  gelatine-plate  cultures.  The  colonies  soon  sink 
in  the  dissolved  gelatine;  they  generally  appear  surrounded 
by  a  more  or  less  fluorescent  zone.  In  gelatine  "  stick  " 
cultures  of  this  kind  the  gelatine  is  dissolved  in  a  funnel 
shape,  and  the  surface  then  first  fluoresces  strongly,  and 
later  is  covered  by  a  greenish  film.  On  agar-agar  a  green- 
ish-white deposit  is  formed.  Even  in  beef -broth  a  green 
coloration  is  observed.  This  bacterium  causes  no  acidity 
in  milk,  but  produces  a  complete  precipitate  of  casein  by 
alkaline  reaction  (seldom  by  neutral  reaction) ;  a  more  or 
less  pronounced  disagreeable  rotten  smell,  furthermore,  ap- 
pears in  the  substratum.  In  many  respects  this  bacterium 
seems  to  resemble  Fliigge's  Bacillus  fluorescens  liquefa- 
ciens.  As  mentioned  above  it  is  often  met  with  in  manure 
particles,  especially  if  these  are  very  moist.  I  have  also 
found  it  in  stagnant  water.  Sunlight  and  even  daylight 
seems  to  kill  the  organism  within  a  short  time. 

2b.  Bacteria  Coagulating  Casein  and  Subsequently 
Peptonizing  the  Coagulum. — This  subdivision  has  not, 
according  to  my  experience,  many  representatives  in  our 
country.  The  bacteria  spoken  of  above  as  resembling 
the  blue-milk  bacillus  belong  here.  Another  represen- 
tative of  this  subdivision  was  found  last  winter  in  a  sam- 
ple of  milk  from  Helsingfors.  The  casein  in  this  milk 
did  not  coagulate,  but  the  whole  milk  assumed  a  jelly- 
like  consistency,  became  fibrous  and  coherent,  and  turned 
a  grayish  and  afterwards  a  brownish  color.  Later  on  this 
jelly-like  mass  gradually  dissolved.  The  bacteria  causing 
these  changes  were  isolated  and  found  to  be  a  long, 
staff -like  bacillus  which  often  appeared  in  coherent  chains. 
Inoculated  in  sterilized  milk  it  produced  a  strong  alkaline 
reaction,  and  otherwise  changed  the  milk  as  stated  above. 


104  MODERtf   DAIRY   PRACTICE. 

Quite  frequently  the  so-called  potato  bacillus — Bacillus 
mesentericus  vulgatus — is  found  in  Finnish  milk.  This  may 
easily  be  recognized  by  its  active  power  of  locomotion,  its 
short,  thick  staff-shape,  its  strong  peptonizing  power,  and 
its  great  inclination  to  build  spores.  I  have  also  found 
represented  in  our  Finnish  milk  the  Duclaux  Tyrothrix 
family,  some  species  of  which  resemble  in  several  respects 
the  potato  bacilli.  The  organisms  belonging  to  this  sub- 
division generally  have  spores  possessing  great  tenacity 
of  life;  they  easily  withstand  boiling  temperatures.  For 
this  reason  their  presence  in  milk  is  very  injurious.  Ac- 
cording to  Duclaux,  the  bacteria  of  this  subdivision  pro- 
duce two  substances :  the  one  which  he  identifies  with  ren- 
net precipitates  casein,  while  the  other  again  peptonizes  it. 

This  subdivision  seems  to  be  more  numerous  in  milk 
produced  in  southern  countries  than  in  our  northern  milk. 
My  investigations  of  South  German  and  French  milk 
would  show  this;  and  also  the  constant  appearance  of  milk 
diseases,  as  red  milk,  blue  milk,  etc.,  which  are  caused  by 
infection  of  bacteria  belonging  to  this  subdivision,  in  sam- 
ples of  milk  examined.* 

Zc.  Bacteria  bringing  Casein  into  Fermentation  with- 
out Coagulating  It. — The  final  result  of  the  activity  in 
milk  of  bacteria  belonging  to  this  subdivision  is  the  same 
as  that  of  the  families  belonging  to  the  last  two  sub- 
divisions, viz.,  a  solution  of  the  casein  through  decom- 
position. These  subdivisions  together  form  the  group  of 
bacteria  called  putrefactive  bacteria  by  older  bacteriologists 

*  For  a  description  of  bacteria  belonging  to  this  subdivision  see 
Scholl,  "Die  Milch,"  1891,  p.  42;  Conn,  "The  Fermentations  of 
Milk,"  1892,  p.  48;  Freudenreich,  "  Bakteriologie  d.  Milch  wirt- 
schaft,"  1893,  p.  45,  etc. 


BACTERIA   COMMONLY   FOUHD   IK   COWS*   MILK.       105 

— a  term  also  used  in  the  following  pages  for  the  sake  of 
brevity.  All  these  bacteria  decompose  albuminoid  sub- 
stances and  produce  an  unpleasant  smell;  the  final  prod- 
ucts in  the  substrata  are  carbonic  acid,  ammonia,  and 
water.  In  the  dairy  they  generally  have  an  injurious  in- 
fluence; some  play  a  part  in  the  ripening  of  certain  kinds 
of  cheese,  however.  They  are  of  the  greatest  importance 
and  value  to  the  agriculturist  in  other  domains,  since 
they  split  up  the  complicated  albuminoids  of  the  manure' 
into  such  substances  as  may  serve  as  nutrients  for  cul- 
tivated plants.  These  bacteria  are  therefore  especially 
numerous  in  solid  and  liquid  manure,  and  their  presence 
in  milk  shows  that  this  has  been  contaminated  with  these 
substances. 

This  applies  especially  to  the  bacteria  included  in  the 
third  subdivision.  The  more  macroscopic  impurities 
coming  from  the  manure,  the  greater  is  the  probability 
that  these  bacteria  will  appear  in  large  numbers.  The 
most  common  of  them  belong  to  the  family  Proteus  (Hau- 
ser),  and  are  characterized  by  a  rapid  power  of  locomotion; 
they  are  often  supplied  with  cilia,  and  generally  somewhat 
curved,  staff-like  bacteria.  They  seem  to  attack  the  casein 
of  the  milk  directly  without  precipitating  it,  and  dissolve  it 
under  decomposition.  Although  they  do  not  develop  spores, 
they  are  very  tenacious  of  life.  They  can  stand  both  pro- 
longed drought  and  a  cold  of  -  4°  to  -  22°  F.  (20°  -  30°  C.). 
The  fermentation  produced  by  these  bacteria  in  milk  gives 
it  sometimes  a  bad  and  insipid,  sometimes  a  bitter,  taste. 
If  the  cream  from  such  milk  is  allowed  to  grow  old  it  will 
yield  a  rotten  odor,  and  air-bubbles  will  form  both  in  the 
inner  portion  and  on  the  surface  of  the  skim-milk. 

All  the  milk  bacteria  enumerated  in  the  preceding  are 


106  MODERN    DAIRY   PRACTICE. 

aerobic,  i.e.,  they  form  first  of  all  in  the  presence  of  air. 
But  anaerobic  bacteria  (i.e.,  such  as  cannot  live  in  an  at- 
mosphere containing  oxygen)  may  also  be  found  in  milk. 
The  examination  of  these  is  unfortunately  attended  by  great 
difficulties.  I  have  found  a  butyric-acid  fermentation 
produced  by  anaerobic  bacilli  in  two  samples  of  milk,  and 
in  several  other  samples  have  found  numerous  anaerobic 
bacteria  causing  putrefactive  fermentations.  By  an  ordi- 
nary aerobic  quantitative  analysis  only  a  very  few  colonies 
appeared  in  these  samples ;  this  was  contrary  to  the  results 
of  a  preceding  microscopic  examination  which  showed  that 
the  milk  was  filled  with  numerous  bacteria.  The  explana- 
tion of  the  apparent  contradiction  was  of  course  that  the 
bacteria  found  in  the  milk  were  largely  anaerobic,  and 
could  not  thus  develop  in  cultures  to  which  the  air  had 
free  access. 

Other  Micro-organisms  in  Milk. — The  short  enumera- 
tion of  the  injurious  bacteria  of  milk  given  in  the  preced- 
ing only  includes  the  bacteria  proper.  Other  micro-organ- 
isms resembling  the  bacteria  are  also  found  in  milk, 
that  may  influence  its  quality.  Among  these  the  yeast- 
fungi  may  be  mentioned.  They  demand  in  the  main  the 
same  conditions  of  life  as  the  bacteria,  are  somewhat  larger 
than  these,  and  oval-shaped.  They  multiply  through  bud- 
ding (Fig.  12),  i.e.,  in  the  manner  that  cell-buds  project 
from  one  or  both  ends  of  the  round  cell.  This  gradually 
grows  until  the  new  cell  reaches  the  size  of  the  mother-cell, 
when  it  either  breaks  off  from  the  latter  by  a  cross- wall,  or 
at  once  begins  to  form  new  buds. 

The  yeasts  appear  comparatively  seldom  in  milk,  and 
only  a  very  few  forms  are  able  to  cause  fermentations  in 
this  medium,  and  thus  injure  its  quality.  I  have  examined 


BACTERIA    COMMONLY   FOUND   Itf   COWS*   MILK.       107 

the  relation  of  a  large  number  of  different  yeasts  in  this 
respect,  and  found  that  only  two  of  them  may  be  consid- 
ered as  enemies  of  the  quality  of  the  milk.  These  produce 
lactic-acid  fermentations,  and  also  form  alcohol  in  it  in 
smallef  or  larger  quantities.  In  "  Saprophytic  Micro-or- 
ganisms in  Cows'  Milk/'  pp.  34-36,  1  have  characterized 
more  fully  these  two  organisms,  which  I  have  named  Sac- 
charomyces  lactis  and  8.  acidi  lactici. 

The  latter  yeast  has  several  times  been  found  by  me  in 
Finnish  milk,  both  in  milk  from  the  Kuopio  and  the 
Joensum  region,  and  in  samples  coining  from  Borgaa. 

Besides  bacteria  and  yeasts,  molds  often  appear  in  milk. 
We  see  mentioned  in  many  text-books  that  the  milk  has 
a  special  mold,  Oidium  lactis.  As  a  matter  of  fact,  how- 
ever, we  very  often  find  organisms  in  the  milk  which  long 
have  had  this  name  in  bacterial  science;  they  are  especially 
found  in  milk  left  to  sour  in  wooden  pans.  Every  sample 
of  sour  milk  of  this  kind  which  I  have  met  with  has  been 
strongly  infected  by  oidium  lactis.  The  fact  seems  to  be, 
however,  that  several  different  moulds  hide  themselves 
under  this  name,  and  that  oidium  lactis  only  signifies  a 
certain  stage  of  development  with  different  moulds  —  a  stage 
when  they  all  have  about  the  same  appearance.  They  ap- 
pear to  the  naked  eye  as  a  fine,  white,  velvet  down  on  the 
milk;  under  the  microscope  they  appear  like  ramified 
threads  separated  by  numerous  cross  walls.  We  shall  in  a 
later  chapter  return  to  the  action  of  these  moulds  in  the 


k- 


CHAPTER  IV. 
CLEANLINESS  IN  BUTTER  AND  CHEESE  FACTORIES. 

THE  sources  of  infection  of  the  milk  while  kept  in  the 
stable  and  during  the  transportation  to  the  factory  have 
been  described  in  the  preceding.  We  shall  now  consider 
the  dangers  of  infection  threatening  the  milk  during  its 
further  treatment  in  the  factory.  The  necessary  cleanli- 
ness and  care  in  receiving,  weighing,  and  straining  or 
keeping  the  milk  in  the  vats  are  as  a  rule  observed  in  the 
modern  dairy  industry.  It  may  be  in  order,  however,  to 
call  attention  to  some  points  in  which  this  principle  is 
occasionally  violated. 

Admittance  to  Factory. — To  begin  with,  the  butter  or 
cheese  maker  ought  to  take  charge  of  the  milk  at  the  door 
of  the  factory,  or  at  least  at  the  door  of  the  separator  or 
milk-room.  Farm  hands  or  drivers  should  not  be  admitted 
into  the  creamery  direct  from  the  work  in  the  barn.  Yet 
we  find  that  in  nearly  all  creameries  in  our  country, 
and  not  seldom  in  foreign  countries,  they  are  at  liberty 
to  visit  any  room  in  the  factory.  I  have  seen  milk- 
drivers  pour  the  milk  into  the  separator-vat,  change 
skim-milk  cans,  etc.  It  is  not  difficult  to  prove  that 
dusty  drivers  carry  legions  of  the  infectious  organisms  of 
the  milk  with  them  into  the  factory,  and  in  their  move- 
ments clouds  of  dust  charged  with  fermentation  spores  are 
set  in  motion. 

108 


CLEANLINESS   IN   BUTTER  AND   CHEESE   FACTORIES.    109 

Clothes  of  Factory  hands. — That  the  factory  hands 
themselves  must  keep  clean  in  the  most  scrupulous  man- 
ner is  a  principle  agreed  to  by  everybody  in  theory,  but 
not  always  duly  followed  in  practice.  It  is  not  fastidious- 
ness to  insist  that  factory  hands  should  appear  dressed  in  a 
white,  easily  washable  costume,  for  only  in  this  case  can  we 
feel  certain  that  they  go  at  their  work  in  a  neat  way,  and 
that  their  clothes  may  not  be  the  cause  of  infecting  the  milk 
or  its  products.  Furthermore,  it  cannot  be  considered  un- 
reasonable to  require  that  persons  working  with  milk  or  milk 
products  to  wear  a  white  cap,  as  it  is  well  known  how  easily 
hairs,  etc.,  may  loosen  from  one's  head.  The  small  coquettish 
caps  placed  on  the  back  of  the  head,  which  are  seen  in  some 
model  dairies  at  expositions,  do  not  accomplish  the  object 
sought.* 

It  is  often  objected  that  it  is  impracticable  for  fac- 
tory hands  to  wear  white  costumes,  as  these  soil  so  quickly, 
for  which  reason  gray  or  blue-striped  clothes  are  recom- 
mended. In  my  opinion  this  objection  shows  in  the  most 
striking  manner  that  white  clothes  alone  ought  to  be  used 
in  butter  and  cheese  factories,  for  any  dirt  on  them  is 
noticeable.  The  first  condition  for  keeping  absolutely 
clean  is,  of  course,  that  filthiness  may  be  observed  and  im- 
mediately removed,  thus  preventing  its  spreading. 

Changing  Clothes. — A  question  which  sometimes  agi- 
tates the  owners  of  factories  is  how  often  the  factory-hands 
ought  to  change  clothes.  As  a  reasonable  rule  in  this 
respect  it  is  often  stated  that  every  factory-man  ought  to 
appear  with  clean  washed  clothes  at  least  every  Sunday 
morning.  According  to  my  experience  from  both  Danish 
and  Finnish  factories,  it  is,  however,  impossible  to  keep  the 

*  In  European  creameries  all  lighter  work  and  the  making  of  the 
butter  are  usually  done  by  women. — "W. 


110  MODERN   DAIRY   PRACTICE. 

clothes  properly  clean  for  a  whole  week,  no  matter  how 
careful  a  person  may  be.  The  only  sensible  rule  in  regard 
to  the  changing  of  wearing  apparel  is  that  clothes  ought 
to  be  replaced  by  clean  ones  as  soon  as  they  become  slightly 
soiled.  It  is  in  my  opinion  necessary  that  factory  hands 
should  have  clean  clothes  every  day  and  every  hour  in  the 
week,  and  not  only  at  the  beginning  of  the  week. 

A  great  difference  may,  as  a  rule,  be  observed  between 
men  and  women  working  in  creameries  in  regard  to  out- 
ward appearance.  We  often  find  that  the  men  are  negli- 
gent as  to  cleanliness  in  wearing  apparel,  etc.,  a  condition 
which  not  seldom  has  led  to  sad  results  as  regards  the 
butter  and  cheese  product.  It  is  of  course  true  that  the 
fact  that  neatness  in  outward  appearance  is  observed  is  no 
guarantee  for  cleanliness  in  general;  but,  on  the  other  hand, 
it  is  always  difficult,  almost  impossible,  for  a  person 
negligent  about  his  looks  to  observe  cleanliness  in  other 
directions.  It  does  not  involve  so  much  expense  for  factory- 
hands  always  to  appear  in  white  and  clean  aprons,  sleeves, 
and  caps,  for  while  laundry  expenses  are  increased,  the  rest 
of  the  clothes  are  protected  by  their  use. 

Necessity  of  Clean  Hands. — The  attention  of  dairy  and 
factory  workers  may  furthermore  be  called  to  the  necessity 
of  keeping  their  hands  carefully  clean,  as  these  very  often 
come  in  contact  with  the  milk,  cream,  and  especially  the 
butter.  I  found  the  following  custom  prevailing  at  a 
margarine  factory  in  France:  Before  beginning  work  in 
which  the  men  came  in  near  contact  with  the  milk  or 
its  products  they  had  to  present  themselves  before  the 
superintendent,  who  then  strictly  examined  them  as  to 
cleanliness,  especially  their  hands. 

Through  the  bacteriological  investigations  of  Mittmann 


CLEANLINESS   IN   BUTTER  AND   CHEESE   FACTORIES.    Ill 

and  others  it  has  been  proved  that  the  frequently  appear- 
ing black  dirt  under  the  finger  nails  contains  a  large  num- 
ber of  different  kinds  of  bacteria.  The  heat  and  moisture 
found  there  are  very  favorable  to  the  growth  of  micro- 
organisms; they  are  highly  fit  to  become  brooding  places 
for  all  kinds  of  bacteria.  Bremer  has  even  shown  the 
presence  of  tubercle  bacilli  in  the  dirt  under  finger  nails, 
and  putrefactive  bacteria  may  easily  be  found  in  it. 

The  Cause  of  the  "  Factory  Odor." — Leaving  the  factory- 
workers  and  turning  our  attention  to  the  factory  itself,  it 
must  first  of  all  be  stated  that  in  most  of  them  (in  almost 
all  older  ones)  the  atmosphere  met  with  is  far  from  pure 
and  sweet.  It  is  heavy  and  moist,  mixed  with  a  character- 
istic odor  which  reminds  one  partly  of  sourness,  partly  of 
musty,  rotting  wood.  This  specific  creamery  (and  cheese 
factory)  odor  is  a  nuisance  in  most  factories.  If  we  look 
around  at  the  floors,  ceilings,  walls,  and  utensils  we  are  not 
in  most  cases  at  a  loss  to  ascertain  the  cause  of  this  condi- 
tion. Fermentation  hotbeds  without  number  may  usually 
be  found,  and  large  colonies  of  moulds  may  be  seen,  as  well 
as  thick  dirt-spots  on  walls  and  ceiling,  and  bad-smelling 
pools  on  the  floor;  in  many  cases  the  drain-gutter  also 
spreads  an  offensive  odor.  Where  such  bad  conditions 
are  not  present,  there  are  others,  more  hidden  ones,  giving 
rise  to  the  foul  atmosphere.  It  is  only  necessary  to  ex- 
amine the  corners  of  the  rooms,  cracks  in  the  floor  and 
wall,  crooks  and  crevices  of  staircases  and  thresholds,  and 
the  explanation  of  the  bad  condition  of  affairs  will  doubt- 
less be  found  there. 

The  Use  of  Water  in  the  Creamery.— A  characteristic 
feature  of  modern  creameries  is  the  superfluity  of  water 
used  in  them;  it  is?  e.g.,  considered  proper  at  any  time  to 


112  MODERN   DAIRY    PRACTICE. 

deluge  the  floor.  Many  and  great  advantages  are  obtained 
by  an  abundant  application  of  water,  but  the  same  ad- 
vantages may,  as  we  shall  see,  be  reached  in  another 
way.  The  main  object  of  this  liberal  use  of  water  in 
creameries  is  to  remove  all  kinds  of  fermentable  fluids 
found  on  the  floor  and  elsewhere.  By  this  means  the 
fermentation-germs  are  removed,  and  under  otherwise 
proper  conditions  the  end  sought  will  also  be  reached. 
The  other  method  for  removing  spilt  fermentative  fluids 
formerly  followed  by  dairymen  also  led  to  good  results, 
especially  where  the  conditions  in  the  creamery  were  some- 
what primitive,  and  where  the  floor  was  not  perfect.  As 
soon  as  some  milk,  whey,  etc.,  was  spilt  on  the  floor  it 
was  carefully  wiped  up,  and  the  place  was  rinsed  with 
a  small  quantity  of  pure  water  which  was  then  also 
wiped  up.  This  method  of  procedure  is  directly  opposite 
to  the  first-mentioned  one,  and  according  to  this  method  the 
creamery  ought  to  be  kept  as  dry  as  possible.  Excellent 
results  are  doubtless  obtained  by  a  careful  observation  of 
this  rule.  On  account  of  the  lack  of  fermentative  fluids 
bacteria  cannot  infest  the  factory,  and  the  air  in  the  whole 
building  is  fresh  and  sweet. 

As  already  stated,  this  method  was  much  thought  of 
during  the  early  days  of  rational  dairying.  Martens  thus 
writes  in  1869  in  his  book  on  the  dairy-farms  of  Schles- 
wig-Holstein :  "  The  drier  the  milk-cellar  is  kept  in  every 
nook  and. corner,  the  highest  cleanliness  being  at  the  same 
time  observed,  the  better  the  milk  will  be  protected  from 
souring.  Any  one  considering  this  too  insignificant  a 
matter  to  deserve  attention  can  never  hope  to  make 
high-grade  butter."  It  cannot  be  doubted  that  this 
method  of  fighting  the  bacteria  "  on  the  dry  way/'  as  it 


CLEANLINESS   IN    BUTTER   AND    CHEESE    FACTORIES.    113 

were,  is  good,  and  it  certainly  would  be  a  great  advantage 
if  it  were  introduced  as  far  as  practicable  also  in  our 
modern  creameries.  It  has  been  objected  that  the  steam- 
ing so  often  applied  in  the  latter  makes  it  difficult  to  fol- 
low this  method;  but  this  difficulty  may  be  obviated  by 
removing  the  steaming  to  a  separate  building,  or  at  least 
to  a  separate  room  in  the  creamery.  The  separator-room 
ought  occasionally  to  be  rinsed  and  even  steamed,  but  also 
here  an  effort  ought  to  be  made  to  keep  the  floors  and  air 
dry;  in  the  other  creamery-rooms  the  floors  should  be 
kept  dry  in  the  daily  work.  The  impropriety  of  putting 
the  wash-room  in  between  the  creamery-rooms,  as  is  the 
case  in  many  creameries,  is  evident  from  what  has  been 
said,  as  well  as  for  other  reasons. 

If  the  rule  is  observed  that  the  steaming  and  rinsing 
are  to  take  place  in  a  separate  room,  there  is  no  reason 
why  the  floors  and  the  air  even  in  our  modern  creameries 
may  not  be  kept  dry.  The  other  difficulties  connected 
with  this  method  are  easily  overcome;  the  same  scrupu- 
lous care  and  neatness  which  formerly  existed  in  the 
creameries  is  necessary.  Strict  cleanliness  can  very  well 
be  observed  in  this  way,  without  the  use  of  large  quantities 
of  water.  In  addition,  regular  and  when  necessary  special 
scrubbings  and  washings  of  floor,  walls,  and  ceiling  must, 
however,  also  be  made. 

The  method  now  commonly  adopted  in  our  creameries, 
viz.,  to  remove  dirt,  milk,  etc.,  from  the  floor  through  a 
liberal  rinsing  with  water,  offers  this  advantage,  that  it 
places  less  demands  on  the  creamery-hands  than  the 
other  method.  This  assertion  is,  however,  in  my  opinion, 
founded  on  a  misunderstanding,  which  is  very  deleterious 
to  the  quality  of  the  dairy  products.  It  says  that  the 


114  MODERN   DAIRY    PRACTICE. 

creamery-man  may  be  relieved  from  paying  attention  to  the 
condition  of  cleanliness  in  detail;  he  has  to  see  to  it  that 
the  rinsing  be  made  thoroughly,  and  the  rest  will  then 
take  care  of  itself.  The  first  man  in  the  creamery  con- 
centrates all  his  efforts  on  the  making  of  the  butter,  the 
running  of  the  separators,  etc.,  and  the  cleaning  up  and 
even  the  supervision  of  the  same  is  left  to  his  helpers, 
while  he  himself  ought  to  care  for  and  look  after  every- 
thing, and  this  first  of  all  as  far  as  the  conditions  of  clean- 
liness are  concerned.  An  abundant  use  of  water  in 
creameries  places  great  demands  on  the  condition  of  the 
creamery-rooms,  as  will  be  seen  from  what  follows. 

We  often  find  larger  or  smaller  cracks  in  the  creamery 
floors;  these  places  are  splendid  culture-beds  for  all  kinds 
of  bacteria.  I  have  amused  myself  by  examining  bacteri- 
ologically  the  fluid  which  stood  in  such  cracks  in  the 
cement  floor  of  a  creamery.  An  astounding  sight  met  my 
eye.  The  large  number  of  species  of  bacteria  and  the 
immense  number  in  which  most  of  them  were  found  ap- 
proached the  incredible.  No  better  object-lesson  can  be 
found  than  such  a  fluid,  if  it  is  desired  to  illustrate  espe- 
cially, to  what  an  extent  an  object  may  be  filled  with  bac- 
teria. The  fluid  will,  of  course,  contain  micro-organisms 
in  proportion  to  the  quantity  of  milk  remains  contained  in 
it.  From  what  has  been  said  it  follows  that  the  creamery 
floor,  above  all  in  a  creamery  where  large  quantities  of 
water  are  used  for  washing,  must  be  tight,  and  even  with- 
out cracks  and  crevices. 

The  Factory  Floor. — These  conditions  are  not  filled  by 
the  cement  floors  generally  used  in  our  creameries.  It  is 
easily  cracked  by  bruises,  and  holes  and  crevices  are  thus 
formed  in  them.  I  have  often  observed  in  creameries, 


CLEANLINESS   IN   BUTTER  AND   CHEESE   FACTORIES.    115 

especially  in  frame  buildings,  that  the  layer  of  cement  has 
loosened  along  the  walls  and  the  crack  thus  formed  has 
been  filled  with  a  dark,  moist  mass,  containing  filth  of  all 
kinds,  and  of  course  bacteria  without  number.  Cement 
floors  are  furthermore  eaten  up  by  lactic  acid  (sour  milk). 
On  account  of  all  this  they  cannot  be  recommended  in 
creameries  where  large  quantities  of  water  are  used  for  rins- 
ing. The  same  holds  true  in  regard  to  floors  of  limestone 
slabs;  the  slabs  have  rarely  a  sufficiently  smooth  surface, 
and  they  often  cannot  be  laid  close  up  to  each  other.  The 
custom  to  lay  these  slabs  as  closely  as  possible  up  to  one 
another  in  loose  sand,  which  is  practised  in  many  places — 
especially  in  foreign  countries — hoping  that  the  interstices 
soon  will  be  filled  with  sand  and  dirt,  must  of  course  be 
absolutely  condemned,  for  infection  hotbeds  are  thereby 
created  all  over  the  floor.  It  is  a  better  practice  to  imbed 
these  slabs  in  cement  so  that  the  interstices  become  filled 
therewith.  I  have,  however,  observed  in  several  creameries 
where  such  floors  are  found  that  the  cement  between  the 
slabs  is  soon  eaten  up  and  gives  way  to  large  gaping  cracks, 
that  gradually  fill  up  with  a  sticky,  filthy  mass.  Wooden 
floors  are  still  more  to  be  rejected.  Through  the  abundant 
washing  they  are  kept  constantly  moist  and  are  apt  to 
soften  and  swell,  after  a  while  allowing  water  mixed  with 
milk  to  run  through  into  the  ground,  where  a  luxurious 
and  injurious  mould  and  bacteria  growth  is  produced  in  the 
dark,  giving  off  bad  odors  and  forming  a  constantly  threaten- 
ing source  of  infection  for  the  milk. 

The  only  creamery-floor  which  in  my  experience  fills 
the  demands  just  given,  and  thus  allows  of  a  flooding  of 
the  floor,  are  those  made  of  a  genuine,  natural  asphalt. 
Such  a  floor  is  firm,  impervious  to  water,  will  not  crack,  is 


116  MODERN   DAIKY   PRACTICE. 

not  attacked  by  acids,  does  not  spread  any  odor,  can  stand 
changes  in  temperature  well,  is  not  cold  to  walk  on,  and 
may  be  easily  kept  clean.  To  all  these  advantages  may 
also  be  added  that  asphalt  floors  are  easily  laid  and  also 
very  easily  and  rapidly  repaired.  It  will  not  be  necessary 
to  interrupt  the  regular  work  in  the  creamery  when  such  a 
floor  is  to  be  laid.  If  we  begin  laying  the  floor  at  noon 
immediately  after  the  day's  work  is  done,  even  the  largest 
floor  may  be  entirely  done  before  the  milk  comes  in  the 
next  morning. 

The  only  disadvantages  of  asphalt  floors  in  creameries 
is  that  asphalt  is  dissolved  by  oils  which  may  drop  from 
the  machinery,  and  that  it  becomes  soft  and  pliable  under 
cans  filled  with  hot  water.  These  disadvantages  may, 
however,  easily  be  avoided  by  a  little  care.  Dripping  of 
oil  ought  in  general  to  be  out  of  the  question  with  dairy 
machinery,  and  the  softening  of  the  asphalt  through  the 
effect  of  hot  cans  may  easily  be  avoided  by  placing  these 
on  a  wooden  stand. 

It  is  important  that  the  creamery  floor  be  laid  at  an 
even  slant  so  that  water  may  drain  off  as  completely  as 
possible.  In  this  respect  the  asphalt  floors  are  also  very 
serviceable;  gutters  may  be  easily  made  in  them,  and  what 
I  consider  very  important,  the  asphalt  may  be  laid  from 
the  floor  up  on  the  wall  at  least  two  feet,  so  that  the  lower 
part  of  the  latter  may  be  impervious  to  water.  By  this 
arrangement  the  part  of  the  wall  most  liable  to  become 
soiled  may  easily  be  kept  clean  through  rinsing  and  wash- 
ing. The  wall  around  the  exit-hole  in  the  wash-room 
should  also  be  dressed  with  asphalt. 

In  planning  and  building  creameries  the  number  of 
corners  and  crooks  that  cannot  be  easily  cleaned  must  be 


CLEANLINESS   IN   BUTTER  AND   CHEESE  FACTORIES.    117 

diminished  as  far  as  possible.  Dark  hiding-places  under 
staircases,  etc.,  floor-drains  which  cannot  be  cleaned  in 
their  whole  length,  and  similar  places  where  infection 
might  start  up,  ought  not  to  be  found.  By  painstaking 
care  in  the  planning  and  building  of  the  factory  we  may 
easily  succeed  in  securing  these  conditions  for  keeping  its 
atmosphere  pure  and  sweet. 

If  a  tight,  smooth,  somewhat  slanting,  acid-proof  floor 
built  as  directed  has  been  secured,  as  abundant  quantities 
of  water  as  may  be  wished  for  can  safely  be  used  in  keeping 
it  clean.  But  how  many  creameries  in  our  country  fulfil 
such  conditions  ?  Many  creameries  have  still  wooden  floors, 
or,  worse  still  (in,  fortunately,  but  few  creameries),  there  is 
only  a  wooden  floor  under  and  around  the  churn  while  the 
rest  of  the  creamery  has  to  do  with  a  dirt  floor.  The  in- 
numerable chances  of  infection  to  which  the  delicate  dairy 
products  are  here  exposed  may  be  easily  imagined.  One 
might  believe  that  the  picture  drawn  applied  to  a  past  era, 
when  dairying  was  still  in  its  infancy;  but  such  is  unfortu- 
nately not  the  case.  I  have  even  found  a  separator  put  in 
a  creamery  with  such  a  floor.  Otherwise  well-equipped 
creameries  also  often  leave  much  to  be  wished  for  as  re- 
gards the  material  and  the  grading  of  the  floor. 

When  the  main  creamery  work  is  done,  about  1  P.M. 
every  day,  all  machinery  and  vessels  as  well  as  the  floors 
are  of  course  cleaned.  The  floor  is  not  washed  until  all 
other  cleaning-  is  finished,  when  it  is  washed  with 
plenty  of  water  and  swept  up  with  a  broom.  Here  and 
there,  however,  some  water  remains  in  holes,  cracks, 
etc.,  and  if  we  enter  the  creamery  an  hour  later  we  shall 
find  the  air  exceedingly  moist,  and  perhaps  pools  of 
water  still  left  on  the  floors.  These  pools  are  often  filled 


118  MODERN   DAIRY   PRACTICE. 

with  bacteria,  especially  if  the  washing  was  done  carelessly 
so  that  inilk  remained  in  them.  To  avoid  this  incon- 
venience the  creamery  floor  should  be  frequently  washed 
with  'boiling-hot  water,  and  the  washing  of  the  floor  at  the 
close  of  the  daily  creamery  work  should  be  followed  by  a 
similar  treatment.  The  floor  will  then  dry  more  rapidly, 
and  there  will  be  no  standing  pools  of  water — at  least  not 
to  such  an  extent  as  by  the  method  now  followed. 

The  great  humidity  of  the  air  in  modern  creameries  in 
connection  with  the  heat  usually  incommoding  them  in 
summer-time  produce  conditions  particularly  favorable  to 
bacteria  and  moulds.  In  many  creameries  we  observe 
various  kinds  of  colored  mould  vegetation  on  walls  and 
under  the  ceiling.  Even  if  spores  and  bacteria  from  these 
colonies  do  not  often  get  into  the  milk  they  will  easily 
infect  vessels  and  apparatus  with  which  the  milk  comes  in 
direct  contact. 

Creamery  Walls  and  Ceilings. — It  is  often  difficult  to 
keep  ceiling  and  walls  properly  free  from  these  growths. 
If  the  creamery  has  stone  walls  they  are  usually  plastered 
and  kalsomined,  and  cannot  therefore  be  washed;  this  is, 
however,  decidedly  a  weak  point.  In  model  creameries 
made  of  brick  I  have  seen  some  rooms  dressed  with  white 
tiles,  which  of  course  did  splendid  service.  The  walls 
could  be  washed  and  scrubbed  as  often  as  desired.  Such 
tile  walls  may,  however,  prove  too  expensive  in  first  cost. 
Two  other  methods  of  dressing  the  walls  are  cheaper,  and 
have  given  satisfaction.  If  the  walls  are  plastered  with 
cement,  smoothed,  and  several  times  finished  with  water- 
glass,  a  waterproof  wall  is  obtained  that  will  stand  rinsing 
and  careful  washing.  Such  a  wall  is  not  so  good  from  the 
standpoint  of  cleanliness,  however,  as  it  is  grayish,  which 


CLEANLINESS   IK   BUTTER  AND   CHEESE   FACTORIES.    119 

in  my  opinion  is  a  serious  drawback,  since  dirt  cannot  at 
once  be  observed  on  it.  Walls  satisfactory  also  in  this 
respect  may  be  obtained  by  painting  the  cemented  and 
smoothed  wall  with  white  oil  paint;  this,  however,  will 
come  a  little  higher  than  applying  a  dressing  of  water- 
glass.  Wooden  walls  may  also  be  made  very  neat  by  being 
painted  white,  and  are  then  easily  cleaned.  The  ceiling  in 
the  creamery-rooms  must  likewise  be  kept  free  from  dirt 
and  bacterial  growth ;  they  had  therefore  better  be  dressed 
in  the  same  way  as  the  walls. 

Airing  of  Apparatus. — All  woodwork  in  the  creamery 
should  be  well  painted.  As  often  as  practicable  all  loose 
wooden  utensils  ought  to  be  carried  outside  into  the  open 
air  and  sunshine,  to  be  dried  and  ventilated.  In  some 
creameries  many  utensils  are  unnecessarily  massive  and 
clumsy,  making  it  difficult  to  carry  them  outside.  The 
creamery-hands  therefore  soon  grow  tired  of  handling 
them  and  leave  off  the  airing  process,  the  result  of  which 
will  soon  be  seen,  however.  I  have  often  in  Finnish  cream- 
eries met  with  large  working  tables  which  have  had 
colonies  of  molds  and  bacteria  on  the  outside;  having  never 
had  a  chance  to  dry  properly  in  the  open  air  they  were  soon 
attacked  by  bacteria.  In  many  creameries  large  and  heavy 
boxes  for  cooling  the  butter  are  now  being  introduced;  the 
small  cooling  boxes  previously  used  were,  in  my  opinion, 
considerably  better,  for  the  reason  given.  Water-soaked 
and  rotting  wood  ought  never  to  be  found  in  butter  or 
cheese  factories.  I  suppose  it  is  from  such  wood  that  the 
peculiar  factory  odor  largely  arises. 

Ventilation  of  Factories. — In  order  to  avoid  the  heat 
in  the  factories  in  summer-time  the  sun  is  usually  shut 
out  by  blinds  or  curtains  at  the  closed  windows.  The 


120  MODERN   DAIRY    PRACTICE. 

heat  is  certainly  diminished  in  this  way,  but  at  the  same 
time  the  creamery  loses  the  disinfecting  influence  of  sun- 
shine and  daylight;  the  darkness  produced  is  favorable  to 
the  bacteria  and  the  ventilation  is  checked.  Awnings  are 
in  some  ways  preferable,  as  the  windows  may  then  be 
kept  open  and  a  draught  created.  Many  creameries  are 
not  ventilate  during  the  day,  but  only  during  the  cool 
evening  and  night.  This  method  cannot,  however,  be 
recommended,  since  the  air  purified  by  sunshine  and  day- 
light is  especially  wanted.  By  ventilating  only  during  the 
night  a  moist  atmosphere  is  let  into  the  creamery,  produc- 
ing a  wet  coating  on  walls  and  ceiling.  A  certain  coolness 
is  obtained  in  this  way,  but  it  is  bought  altogether  too 
dearly.  A  cool  atmosphere  may  be  produced  in  the 
creamery,  e.g.,  in  the  same  way  as  in  breweries — by  means 
of  refrigeration  machines  producing  cold  and  dry  air.  An 
apparatus  which  I  have  seen  used  in  a  small  brewery,  and 
which  ought  to  be  adapted  to  creameries,  is  the  LuftkiiJil- 
apparat,  patent  Honerla.  It  is  simple  and  easily  worked; 
by  means  of  a  fan  the  air  is  forced  into  a  funnel-shaped 
iron  vessel  where  the  cooling  material  (ice)  is  kept.  The 
lower  part  of  the  vessel  is  divided  into  several  compart- 
ments by  shelves,  between  which  the  melted  water  runs 
down  and  the  air  rises  up  toward  the  ice.  The  air  is  thus 
comparatively  cold  when  it  reaches  the  ice,  and  a  too  rapid 
melting  is  avoided.  If  the  ice  be  mixed  with  one-tenth 
part  of  salt,  the  cooling  becomes  still  more  effective.  The 
apparatus  is  comparatively  cheap  (about  $125). 

As  the  creamery-rooms  may  be  kept  properly  cool  by  the 
use  of  this  or  similar  apparatus,  it  is  not  necessary  to  venti- 
late less  on  account  of  the  heat.  The  admission  of  large 
quantities  of  pure  fresh  air  into  the  creamery-rooms  is  one  of 


CLEANLINESS  IN   BUTTER  AND   CHEESE   FACTORIES.    121 

the  best  means  of  working  against  the  spreading  of  factory 
odor.  All  rooms  ought  to  have  ventilators,  preferably 
both  at  the  floor  and  the  ceiling,  and  should  be  supplied 
with  large  windows  which  may  be  opened. 

The  effort  to  keep  the  air  in  the  cheese  or  butter  fac- 
tories pure  may  be  made  very  difficult  and  sometimes  even 
impossible  by  an  irrational  arrangement  of  the  various 
rooms  in  the  factory.  We  find  in  many  places  that,  e.g., 
the  cheese-room  is  directly  adjoining  the  churning  or 
separator-room,  although  it  is  plain  that  the  very  bacteria 
active  in  the  ripening  of  the  cheese  are  the  worst  enemies 
to  the  keeping  quality  of  the  milk  and  butter,  and  may 
easily  infect  the  adjoining  rooms.  We  often  see  even  the 
engine-room,  with  its  atmosphere  filled  with  soot  and  odor 
of  oil,  directly  joining  the  separator-room;  and  frequently 
we  find  the  room  of  the  creamery -man  opening  into  the 
milk-room.  Bad  arrangements  of  the  rooms  may  plainly 
be  fatal  to  the  products  made  there,  and,  like  a  secret  dis- 
ease, all  the  time  prevent  the  business  from  paying. 

The  Surroundings  of  the  Factory. — In  connection  with 
the  question  of  the  necessity  of  fresh  air  stands  the  rule 
that  every  factory  ought  to  have  neat  surroundings,  a 
rule  against  which  nearly  every  factory  in  our  country 
sins  in  one  way  or  another.  In  order  to  obtain  purer 
air  in  the  factory  through  ventilation  it  is,  however,  essen- 
tial that  the  air  outside  be  purer  than  that  inside.  In 
spite  of  this  but  little  care  is  in  most  cases  taken  of  the 
many  conditions  which  may  infect  the  air  in  the  vicinity 
of  the  factory.  A  few  examples  will  illustrate  the  truth 
of  this  statement. 

Drainage. — What  is  the  usual  manner  by  which  the 
wash  and  drain  water  when  once  outside  of  the  creamery 


122  MODERN   DAIRY   PRACTICE. 

wall  is  prevented  from  stagnating  and  spreading  bad 
odors  ?  In  numerous  instances  no  effort  whatever  is  made 
to  prevent  it.  In  the  worst  cases  slop-water  is  allowed 
simply  to  run  under  the  floor  and  from  there  spread  odors 
and  infectious  bacteria  by  the  million.  At  other  factories, 
again,  it  is  left  to  stagnate  just  outside  of  the  building  and 
even  dry  off  there,  which  of  course  causes  the  soil  to  be 
mixed  with  enormous  masses  of  bacteria;  when  the  wind 
sets  the  air  in  motion  immense  quantities  of  infectious 
matter  gain  access  to  the  factory  through  windows,  venti- 
lators, and  doors.  This  immigration  of  bacteria  from  the 
outside  may  also  take  place  in  other  ways.  According  to 
my  observations,  many  bacteria  especially  injurious  to  the 
quality  of  the  milk  usually  thrive  in  such  stagnating  factory 
slop-water.  I  have  found  species  of  tyrothrix  in  such  water, 
and  also  other  of  the  putrefactive  bacteria  enumerated  in 
the  preceding  chapter. 

The  proper  drainage  of  the  slop-water  is  therefore  of 
the  greatest  importance.  Sub-earth  sewers  are  in  most 
cases  to  be  rejected,  since  it  is  almost  impossible  to  keep 
them  properly  clean.  Only  in  cases  where  they  can  be 
properly  cleaned  by  steam  ought  they,  in  my  opinion,  to  be 
tolerated.  Open  sewers  seem  better,  being  more  easily 
cleaned  and  watched.  In  the  Danish  bill  concerning 
Co-operative  and  Proprietary  Creameries  (1888)  it  is  speci- 
fied that  "the  slop-water  is  to  be  conducted  from  the 
creamery  by  paved  or  cemented  gutters  or  glazed  tile  with  a 
sufficient  fall,  to  water-proof  brick  cisterns  situated  at  least 
100  feet  away  from  the  creamery  building,  its  well,  and  other 
buildings,  provided  they  are  occupied."  "  The  cisterns  must 
be  cleaned  and  disinfected  according  to  the  further  direc- 
tions of  the  inspection  committee  "  (Sanitary  Commission). 


CLEANLINESS   IN   BUTTER  AND   CHEESE   FACTORIES.    123 

Location  of  Factories. — We  see  the  proof  of  how  poorly 
is  understood  the  importance  of  the  proper  removal  of 
drainage  water  for  the  successful  conduct  of  the  creamery 
business;  in  creameries  being  situated  so  as  to  make  it  im- 
possible to  get  rid  of  the  slop-water  without  great  expense. 
At  such  places  as  these  no  creamery  should  of  course  ever 
have  been  built.  It  is  evidently  absolutely  impossible  to 
keep  the  air  pure  and  fresh  in  a  creamery  located  near 
a  barn  yard  or  a  hog  pen.  It  is  not  so  generally  under- 
stood as  we  a  priori  should  suppose,  however;  for  here 
and  there  we  find  creameries  whose  location  testifies  to 
the  ignorance  of  the  owner  in  regard  to  this  simple 
point.  In  the  Danish  bill  just  mentioned  the  distance 
required  between  the  creamery  and  hog-pen  is  at  least  50 
feet.  Another  mistake  often  made  in  locating  a  creamery 
is  to  place  it  at  a  lower  point  than  the  barn  and  manure- 
pile.  On  a  dairy  farm  in  our  country  I  found,  e.g.,  that 
the  liquid  manure  drained  off  alongside  the  creamery, 
the  ventilation  of  which  was  largely  from  the  side  where 
the  drainage  went. 

Even  at  factories  where  such  glaring  mistakes  as  those 
mentioned  cannot  be  found,  there  is  often  one  thing  or 
another  to  criticise  concerning  the  location.  We  thus 
often  see  the  factories  erected  close  up  to  the  highway, 
from  which  dust  clouds  during  the  summer  are  scattered 
by  teams  and  wagons.  That  a  serious  infection  of  the 
milk  may  arise  from  rOad  dust  is  plain  from  the  fact  given 
by  Maggiora  that  one  gram  of  road  dust  (^  of  an  ounce) 
at  Turin  usually  contains  not  less  than  78  millions  of 
bacteria.  By  investigations  in  our  country  I  have  never 
obtained  as  high  figures,  but  my  analyses  have  also  shown 
that  road  dust  contains  immense  quantities  of  bacteria, 


124  MODERN    DAIRY   PRACTICE. 

and  I  have  found  among  these  such  as  may  injure  the 
keeping  quality  of  the  milk.  If  a  factory  is  located  too 
near  the  roadside  it  is  furthermore  impossible  to  under- 
take the  very  necessary  airing  of  utensils — a  disadvantage 
which  is  by  no  means  of  small  importance. 

It  is,  however,  absolutely  necessary  to  be  able  to  reach 
the  factory  with  teams.  To  avoid  infection  through  dust 
the  road  up  to  the  factory  should  be  paved,  and  during  hot 
days  sprinkled  and  swept.  It  is  greatly  to  be  recom- 
mended to  plant  trees  and  keep  a  lawn  around  the  factory. 
Close  up  to  the  factory  there  must  not  be  tall  trees,  how- 
ever, as  they  will  throw  too  much  shadow,  and  prevent  the 
light  from  properly  purifying  the  factory  air.  Large 
groups  of  shrubs  keep  the  ground  moist,  and  if  near  the 
wall  will  produce  rot  and  moldiness.  A  small,  neat,  orna- 
mental garden  with  old  linden  trees  and  some  groups  of 
flowers  and  shrubs  here  and  there  has  this  further  advan- 
tage, that  they  not  only  increase  the  feeling  of  well-being 
of  the  factory  hands,  but  also  to  a  great  extent  sharpen 
their  eye  and  sense  for  neatness  and  good  looks. 

It  is  very  difficult  to  keep  a  factory  clean  for  any  length 
of  time  in  a  dirty  and  poorly  kept  location:  even  if 
it  is  nice-looking  and  neat  when  built,  so  that  it  forms  a 
real  oasis  of  cleanliness  among  the  disorder  of  the  sur- 
roundings, it  will  pretty  soon  be  impossible  for  the  factory- 
hands  to  keep  it  so.  Their  eye  for  neatness  and  cleanli- 
ness will  be  gradually  dulled,  the  fight  against  filth  be- 
come more  and  more  hopeless  every  week,  and  finally  they 
meet  and  become  accustomed  to  slovenliness  in  the  factory 
itself. 

The  Farm  Dairy. — On  many  farms  the  dairy  house  is 
also  used  for  other  purposes  than  those  for  which  it  is 


CLEANLINESS   IN   BUTTER  AND    CHEESE   FACTORIES.    125 

intended.  I  need  hardly  mention  the  mistake  of  using 
it  for  the  storage  of  all  kinds  of  food  articles,  as  is  the 
custom  at  many  smaller  farms  ;  these  fill  the  air  with  the 
smell  of  food,  which  is  easily  communicated  to  the  milk; 
with  the  articles  of  food,  molds,  dust,  etc.,  are  furthermore 
often  brought  into  the  dairy. 

A  mistake  of  similar  nature,  which  we  are  surprised  to 
find  also  at  many  large  places  and  which  cannot  be  too 
strongly  condemned,  is  that  the  washing  takes  place  in  the 
dairy.  The  dairy  stands  vacant  for  several  hours  every 
day,  but  if  it  is  used  for  washing  and  steaming  of  clothes 
during  the  interval  it  cannot  be  properly  dried  out  and 
aired  before  the  dairy  work  again  begins.  And  what  is 
still  worse,  by  using  the  dairy  for  this  purpose  a  great 
deal  of  dirt  and  infectious  material  is  brought  into  the 
dairy.  There  can  be  no  doubt  that  typhoid  and  other 
disease  bacteria  have  in  this  manner  found  their  way  into 
the  milk.  It  must  therefore  be  pronounced  a  gross  mis- 
take in  the  dairyman  if  he  permits  the  use  of  the  dairy 
for  this  purpose. 

Disinfection  of  Factories. — In  spite  of  all  care  and  pre- 
cautions the  bacteria  will  sometimes  get  the  upper  hand 
in  some  butter  and  cheese  factories.  In  well-conducted 
factories  this  ought  never  to  happen,  but  many  of  them 
are  so  arranged  and  equipped  that  it  is  impossible  to  ob- 
serve the  rules  of  cleanliness  in  all  respects  in  them.  At 
such  places  where  the  bacterial  growth  cannot,  then,  be 
checked  by  ordinary  means,  it  is  necessary  to  fight  the 
bacteria  directly  by  arranging  a  disinfection  of  the  factory 
or  parts  of  it.  We  note  in  this  connection  that  in  dairy 
practice  disinfection  is  often  confounded  with  deodoriza- 
tion.  It  is  not  sufficient  to  destroy  the  odors  which  putre- 


126  MODERN   DAIEY   PEACTICE. 

factive  and  other  fermentative  processes  produce  in  the 
creamery,  but  the  bacteria  themselves  must  be  killed  or 
their  development  and  reproduction  must  be  checked. 
Disinfection  must  therefore  be  considered  far  more  im- 
portant than  deodorization;  the  latter  cannot,  however,  be 
neglected  in  the  dairy  practice,  for  dairy  products,  especially 
milk,  are  extremely  sensitive  to  all  odors. 

On  account  of  this  sensitiveness  a  good  many  disin- 
fectants, as  carbolic  acid,  chloride  of  lime,  etc.,  cannot  be 
used  for  factory  disinfection.  Nor  is  it  advisable  to  make 
use  of  poisons,  as  corrosive  sublimate,  in  the  disinfection 
of  a  butter  or  cheese  factory,  although  these  are  very 
effective.  • 

Lime  is  used  at  several  factories  as  a  disinfectant, 
especially  in  case  of  acidity  in  milk  utensils,  etc.  The 
disinfecting  quality  of  this  substance  is,  however,  compara- 
tively small.  Liborius  concludes  from  lengthy  investiga- 
tions that  lime-water  checks  the  development  of  micro- 
organisms, but  cannot  destroy  them  completely.  Migula 
recommends  to  disinfect  the  yard  outside  the  factory,  floors, 
etc.,  by  a  repeated  sprinkling  of  a  freshly  prepared  solu- 
tion of  slaked  lime. 

Chloride  of  Lime  is  applied  in  breweries  for  this  pur- 
pose, but  both  on  account  of  its  strong  odor  and  its  cost  it 
will  not  be  found  adapted  to  creameries.  Vitriol  of  zinc 
is,  on  the  other  hand,  a  very  suitable  disinfectant;  it  is  re- 
ported to  kill  bacteria,  and  is  also  cheap.  Other  vitriols,  as 
copperas  and  blue  vitriol,  may  also  advantageously  be  used, 
since  they  not  only  destroy  bacteria,  but  prevent  the  rise 
of  bad  odors  in  the  creamery.  On  account  of  its  poisonous 
character  blue  vitriol  must  be  applied  with  care;  copperas 
is  cheap.  Alexander  MuJler  recommends  a  preparation 


CLEANLINESS   IN   BUTTER   AND   CHEESE   FACTORIES.    127 

made  at  Meyer  &  Kiemann's  chemical  factory  in  Hamburg 
for  application  in  creameries,  containing 

Sol.  iron  sulf  ate 63$ 

Iron  oxide 17$ 

Chem.  combined  water 20$ 

This  powder  is  mixed  with  about  20  parts  of  water  in  a 
wooden  pail,  the  mixture  stirred  and  used  after  standing  for 
a  while,  until  the  precipitate  does  not  color  the  water  yel- 
low or  until  the  water  no  longer  gives  a  distinct  taste  of 
ink.  After  having  been  well  washed  the  floor  is  sprinkled 
with  the  mixture  by  means  of  a  broom,  and  then  rinsed 
with  pure  water.  If  the  sewer-pipes  and  sewer-boxes  are 
not  deodorized  through  the  action  of  the  disinfecting 
fluid,  some  of  the  vitriol  is  sprinkled  in  them  in  solid 
form.  In  applying  this  chemical  it  may  be  noted  that 
clothes  or  wooden  materials  with  which  it  comes  in  contact 
will  be  colored  brown  from  the  iron  in  the  liquid. 

Chlorin  Gas  may  be  applied  for  deodorization  as  well 
as  for  disinfection;  potassium  permanganate  is  however, 
to  be  preferred,  and  does  splendid  service.  If  substances 
possessing  bad  odor  or  taste  are  dipped  into  a  weak  solution 
of  permanganate  they  will  be  freed  from  these  undesirable 
qualities.  The  substance  is  entirely  harmless,  but  is  un- 
fortunately comparatively  expensive. 

Water  for  Factory  Purposes. — As  is  apparent  from  the 
preceding,  water  plays  an  important  part  in  the  manage- 
ment of  the  dairy  business,  and  it  may  therefore  be  in 
order  to  further  explain  the  conditions  which  influence  its 
quality. 

If  sufficient  quantities  of  spring-water  or  good  well- 
water  are  at  hand  it  is  comparatively  easy  to  keep  the 


128  MODERN   DAIBY   PRACTICE. 

creamery  clean.  But,  especially  during  the  spring  floods, 
many  of  our  factories  have  to  be  satisfied  with  an  impure 
water,  rich  in  micro-organisms  which  may  directly  con- 
tribute to  the  infection  of  the  factory. 

As  we  have  seen  before,  water  is  generally  an  excellent 
nutritive  medium  for  a  large  number  of  bacteria,  which 
thrive  the  better  in  it  the  more  it  is  polluted  with  organic 
substances  and  the  less  it  is  exposed  to  the  air.  We  often 
see  brick-laid  wells  covered  so  that  ventilation  is  rendered 
entirely  impossible.  I  have  heard  complaints  of  the  quality 
of  the  water  at  every  factory  where  I  found  this  was  the 
case.  In  the  Danish  bill  for  Co-operative  and  Proprietary 
Creameries  previously  mentioned  it  is  stipulated  that  the 
wells  of  the  creameries  should  be  located  in  such  a  way  as 
to  prevent  impure  water  from  flowing  into  them.  New 
creameries  are  to  be  located  only  where  plenty  of  good 
water  may  be  obtained. 

The  solid  particles  and  impurities  found  in  the  wells 
seem  to  affect  the  bacteria  content  of  the  water.  It  has 
been  proved  by  special  investigations  that  bacteria  in  wells 
multiply  best  in  the  immediate  neighborhood  of  solid 
matters,  even  if  these  are  as  unfit  for  nutrients  as  stones. 
A  properly-kept  well  ought  therefore  to  be  free  from  all 
unnecessary  solid  substances.  It  is  further  of  importance 
that  the  well  be  not  long  left  unused.  The  best  way  to 
keep  the  water  pure  in  a  well  is  of  course  to  empty  it  as 
often  as  possible.  Heraeus  says  on  this  point:  The  best 
well  may,  if  used  only  a  little  or  not  at  all,  yield  water  with 
thousands  of  bacteria  capable  of  reproduction  in  every 
cubic  centimeter,  and  the  poorest  well  may  be  so  improved 
by  continual  pumping  that  its  water  will  contain  but  few 
bacteria. 


CLEANLINESS  IN   BUTTER  AND   CHEESE   FACTORIES.    129 

The  bacteria  content  of  well-water  depends  to  a 
large  extent  on  its  origin.  If  it  comes  directly  from  the 
surface  it  will,  especially  during  the  hot  season,  be  very 
rich  in  bacteria,  since  surface-water  generally  goes  through 
fields,  roads,  and  other  places  rich  in  bacterial  life.  In  a 
good  many  of  our  factories  this  danger  of  surface-water 
leaking  into  the  well  has  not  been  realized.  Such  water 
may  in  several  creameries  run  directly  into  the  well  or 
down  through  the  leaky  woodwork;  this  explains  why 
many  creamery-men  complain  that  they  cannot  use  the 
well-water  after  a  heavy  rain. 

Even  if  the  surface-water  does  not  run  into  the  well, 
the  water  may  contain  bacteria  in  large  number,  according 
to  the  stratum  of  the  earth  from  which  it  is  derived. 

The  earth  acts  on  the  whole  as  a  filter,  retaining  the 
bacteria.  We  therefore  find  the  largest  number  of  such 
organisms  in  its  upper  layers.  In  the  surface  layer  of 
sandy  soil  (in  Berlin)  Frankel  found  45,000-350,000  bac- 
teria per  cubic  centimeter,  while  Keimers  in  the  surface 
layer  of  a  clayey  soil  (in  Jena)  found  160,000-2,500,000 
per  cubic  centimeter;  both  investigators  ascertained  that 
the  largest  quantity  was  not  found  directly  on  the  surface, 
but  a  little  below  the  same — a  fact  which  is  perhaps  ex- 
plained by  the  fatal  action  of  the  light  on  the  surface  bac- 
teria. From  maximum  at  a  few  inches  below  the  surface 
the  bacteria  content  of  the  soil  decreases  rapidly  as  we  go 
down.  Frankel  found  only  200-2000  bacteria  in  soil 
three  feet  deep,  and  four  and  a  half  feet  below  the  sur- 
face the  soil  was  generally  free  from  bacteria.  In  Jena 
absolute  sterility  of  the  soil  does  not  appear  until  at  a 
depth  of  six  feet.  These  facts  corroborate  the  observation 
made  by  both  investigators  mentioned,  that  the  deep 


130  MODERN   DAIRY    PRACTICE. 

water  proper  is  always  free  from  bacteria.  Frankel's  in- 
vestigations show  that  this  is  the  case  even  where  the 
water  is  derived  from  strata  of  the  earth  under  highly 
polluted  places.  Artesian  well-water  is  therefore  as  a  rule 
sterile. 

The  water  in  a  creamery  well  ought  of  course  prefer- 
ably to  come  from  deep-soil  layers.  By  digging  a  deep 
well  another  advantage  is  secured  from  the  fact  that  the 
deeper  the  layer  from  which  the  water  comes  the  colder  it 
naturally  is,  and,  as  is  well  known,  a  low  temperature  will 
check  the  bacteria  to  a  large  extent.  In  comparing  the 
rapidity  in  the  development  of  the  same  kind  of  bacteria 
from  the  upper  strata  of  soil  and  from  lower  strata 
Reimers  found  that  the  latter  showed  a  considerably  slower 
development  ( Wachsthumsverlangsamting)  than  the  former 
— a  relation  which  appeared  the  sharper  the  deeper  the 
well. 

In  case  of  doubt  whether  the  water  available  in  a 
creamery  is  fit  for  use,  it  will  not  do  to  make  only  a  chem- 
ical examination,  but  it  must  also  be  analyzed  bacteriolog- 
ically.  The  difficulty  with  the  latter  examination  is,  that 
the  sample  must  be  analyzed  as  soon  as  taken.  It  cannot 
therefore  be  sent  away  for  bacteriological  examination,  but 
the  bacteriologist  himself  must  take  the  sample  and  begin 
the  analysis  at  once.  If  the  bacteria  in  the  sample  get 
time  to  increase  before  the  examination  is  made,  it  will 
not  be  possible  to  find  the  original  bacterial  content  of  the 
same.  Owing  to  the  fight  between  the  different  kinds  of 
bacteria  mentioned  in  the  preceding  chapter,  the  true  rela- 
tion between  the  different  forms  can  then,  furthermore, 
not  be  ascertained — a  point  which  is  of  course  important 
in  judging  the  applicability  of  the  water.  Heraeus  fixes 


CLEANLINESS   IN    BUTTER  AND   CHEESE   FACTORIES.    131 

as  a  standard  for  good  drinking  and  well-water  that  it 
must  not  contain  more  than  500  bacteria  capable  of  de- 
velopment per  cubic  centimeter.  Plagge  and  Proskauer 
consider  the  upper  limit  300  per  cubic  centimeter,  while 
others  place  the  standard  still  lower. 

The  milk  and  its  products  often  come  into  most  inti- 
mate contact  with  water  in  the  factory.  Small  portions  of 
water  will  remain  in  every  can,  in  the  churn,  in  vats,  on 
the  worker,  etc.,  so  that  the  milk  throughout  its  handling 
and  manufacturing  may  be  infected  by  bacteria  found  in 
the  water.  It  will  not  therefore  be  surprising  that  we  have 
dwelt  at  length  on  the  importance  of  the  quality  of  the 
water  in  the  factory  and  the  care  of  the  well. 

Purification  of  Water.— It  would  of  course  be  preferable 
to  entirely  remove  the  bacteria  from  the  water  to  be  used 
in  the  factory,  but  this  would  be  too  expensive.  Breyer's 
"  micro-membrane  filter  "  is  recommended  by  several  parties 
for  use  in  factories  and  is  said  to  deliver  sufficient  water. 
The  water  is  in  this  apparatus  filtered  through  specially 
prepared  asbestos  disks.  Chamberland's  filtering  apparatus 
also  performs  this  cleaning  process  very  well,  but  the  ca- 
pacity of  the  apparatus  is  generally  much  too  small  to  be 
adapted  to  factory  use.  At  all  events  it  is  so  expensive  to 
remove  bacteria  from  the  water  by  such  apparatus  that  it 
will  hardly  be  generally  adopted  in  factories. 

It  is,  however,  the  duty  of  every  factory-man  to  keep 
the  water  in  the  factory  as  pure  and  free  from  bacteria  as 
possible.  He  must  first  of  all  see  to  it  that  the  well  fulfils 
fair  demands  in  regard  to  the  conditions  mentioned,  and 
that  the  water  is  always  used  as  soon  as  pumped.  By 
standing  in  the  warm  factory  a  far  greater  number  of  bac- 
teria may  develop  in  the  same  than  was  originally  found  in 


132  MODERN   DAIRY   PRACTICE. 

it.  In  some  cases  it  will  prove  of  advantage  to  free  the 
water  from  coarse  impurities  by  means  of  a  sand  or  animal- 
charcoal  filter.  A  simple  and  practical  water-filter  has 
been  constructed  by  Paasch  in  Horsens,  Denmark.  In  an 
iron  cylinder  about  three  feet  high  and  one  foot  wide  were 
placed  six  different  layers,  viz.,  small  pebbles,  gravel,  sand, 
charcoal,  rusty  bits  of  iron,  etc.;  the  layers  were  sepa- 
rated from  one  another  by  means  of  perforated  false 
bottoms.  The  apparatus  is  very  easily  cleaned  and  kept  in 
order. 

The  water  used  for  rinsing  vessels  in  which  milk  or  its 
products  are  to  be  handled  ought  in  one  way  or  another  to 
be  made  germ-free.  If  allowed  to  evaporate  in  or  on  the 
utensils  it  leaves  on  them  not  only  all  visible  impurities 
it  may  happen  to  contain,  but  also  substances  invisible 
to  the  naked  eyes,  as  bacteria.  The  special  treatment 
necessary  for  preventing  infection  by  the  water  may,  in 
my  experience,  be  of  two  kinds.  The  more  common  way 
in  dairy  work  is  to  sterilize  the  water  through  boiling  be- 
fore using  it;  where  boiled  water  cannot  be  used,  melted 
ice-water  with  pieces  of  ice  still  floating  in  the  same  is 
often  applied. 

Sterilization  of  Water. — Both  these  methods  may  be 
recommended  for  factory  purposes.  The  boiling  is  done 
by  heating  water  with  steam  in  clean  tin  cans  after  finish- 
ing the  other  work  of  the  day;  the  cans  are  then  covered 
so  that  dust  cannot  get  into  them,  and  the  water  is  cooled 
as  rapidly  as  possible.  The  majority  of  the  bacteria  and 
spores  found  in  it  will  be  killed  by  this  treatment,  and  the 
development  and  multiplication  of  the  few  surviving  ones 
will  be  checked. 

Use  of  Ice-water. — The  method  of  applying  ice-water 


CLEANLINESS   IK   BUTTER  AND   CHEESE   FACTORIES.    133 

in  dairy  work  must  be  spoken  of  a  little  more  at  length. 
Many  investigators  have  proved  that  ice  may  contain  a 
large  number  of  bacteria.  Frankel  found  ice  from  the  river 
Spree  to  contain  between  20  and  6000  bacteria  per  cubic 
centimeter.  Ice  from  rivers  and  lakes  close  by  cities  and 
factories  will  contain  a  large  number  of  bacteria;  conditions, 
as  whether  the  ice  sampled  was  formed  near  by  the  shore  or 
out  in  the  open  lake,  at  the  surface  or  farther  down,  will  also 
cause  great  variability  in  the  results  found  by  analysis. 

Bacteria  in  Ice. — Although  we  may  find  a  considerable 
number  of  bacteria  in  ice  under  certain  conditions,  it  is, 
however,  a  fact  that  every  time  water  freezes  its  bacterial 
content  is  considerably  diminished.  FrankeFs  investiga- 
tions show  this  plainly.  Water  from  the  river  Spree 
containing  6000  bacteria  per  cubic  centimeter  froze  at 
10°-18°  F.  After  two  days  one  cubic  centimeter  con- 
tained only  1200  bacteria,  and  after  nine  days  only  14.  In 
another  sample  3300  bacteria  were  found  per  cubic  centi- 
meter at  the  beginning  of  the  experiment  and  after  three 
days'  freezing  only  20  bacteria  in  the  same  volume.  A 
third  sample,  which  was  highly  infected  with  bacteria,  con- 
taining not  less  than  500,000  bacteria  per  cubic  centimeter, 
showed  only  36,000  per  cubic  centimeter  after  six  days' 
freezing.  The  freezing  is  therefore  a  powerful  means 
against  the  development  of  the  bacteria  in  the  water.*  It 
is  in  reality  of  no  great  importance  that  absolute  sterility 
cannot  be  obtained  in  the  water  in  this  way,  as  the  bacterial 
content  by  this  method  will  be  extremely  small,  provided 
the  water  is  not  highly  infected  before  the  freezing. 

In  the  bacteriological  analysis  of  ice  which  I  have 
made  I  have  obtained  greatly  varying  results,  according  to 
*  See  foot-note  on  p.  134. 


134  MODERN  DAIRY  PRACTICE. 

the  origin  of  the  ice.  In  examining  thick  lake  ice  in  the 
centre  of  a  large  block  of  ice  the  analyses  proved  it  to  be 
entirely  free  from  bacteria.  On  the  surface  of  this  block, 
which  was  exposed  to  infection  during  the  cutting,  haul- 
ing, etc.,  an  appreciable  quantity  was,  on  the  other  hand, 
found  ranging  from  20  to  400  per  cubic  centimeter.  Only 
one  inch  deep  no  bacteria  was  usually  found ;  sometimes, 
however,  a  couple  of  bacteria  colonies  appeared  on  the 
gelatine  plates  in  the  bacteriological  analyses.  The  block 
of  ice  was  taken  from  the  lake  in  March  and  hauled  to  an 
ice-house;  the  analyses  were  made  in  the  following  August. 
Even  porous,  soft  ice  has  proved  very  poor  in  bacteria, 
sometimes  entirely  sterile,  if  it  did  not  come  from  the 
surface  layer.  This  was  found  to  be  the  case  in  ice  taken 
from  a  lake  where  no  city  or  factory  was  situated.  The 
results  of  analyses  made  of  ice  from  the  harbor  of  Helsing- 
fors  were  different.  They  showed  that  the  water  must 
have  been  very  rich  in  bacteria  before  the  freezing,  for 
about  two  months  after  the  harbor  was  frozen  over,  the  ice 
contained  between  260  and  3500  bacteria  per  cubic  centi- 
meter. The  material  for  these  analyses  was  taken  by 
myself  from  the  ice  in  the  harbor.  No  ice  free  from 
bacteria  was  found  in  this  place.* 

*  Russell  (Med.  News,  Aug.  17,  1889)  gives  bacteriological  analy- 
ses of  ice  from  Mendota  Lake  (near  Madison,  Wis.).  No  factory 
is  found  on  the  shores  of  this  lake,  but  it  receives  a  good  share  of 
the  sewage  from  about  15,000  people.  The  number  of  bacteria 
per  cubic  centimeter  of  ice  varied  greatly,  viz.,  in  62  trials  from  14 
to  1249,  the  average  number  being  270.  The  bacteria  content  of 
the  lake  water  varied  from  3  to  3167,  the  average  being  684  per  cc. 
About  60  per  cent  of  the  bacteria  were  thus  lost  by  the  freezing. 
Prudden  (Med.  Eecord,  31,  344  ;  see  loc.  cit.)  claims  that  90  per  cent 
are  destroyed  by  freezing ;  while  Fraukel  (Zeit.  f.  Hyg.,  1,  308)  has 


CLEANLINESS   IN   BUTTER  AND   CHEESE   FACTORIES.    135 

My  investigations  concerning  the  bacteria  of  ice  have 
also  proved  another  fact,  which  still  more  confirms  my 
opinion  that  recently  melted  ice-water  is  to  be  preferred 
even  to  very  pure  well-water  in  the  dairy  work.  The  in- 
vestigations showed  that  in  case  of  bacteria  remaining  in 
the  ice  for  a  long  time  their  virulence,  i.e.,  their  power  to 
develop  their  specific  qualities,  was  greatly  diminished. 
Their  multiplication  took  place  very  slowly,  and  where  the 
bacteria  were  made  up  of  fermentation-starters,  the  fer- 
mentation developed  considerably  more  slowly  and  less 
intensely  than  was  usually  the  case.  I  also  observed 
that  some  of  the  ice-water  bacteria  which  did  not  show 
any  fermentative  power  on  the  first  inoculation  cultures, 
after  having  later  reached  their  normal  conditions  again 
possessed  this  power.  The  investigations  were  made  both 
with  lactic-acid  bacteria  and  putrefactive  bacteria.  The 
former,  which  caused  a  complete  fermentation  in  milk 
before  the  freezing  by  being  kept  for  twenty-four  hours  in 
an  incubator  at  86°  F.  (30°  C.),  were  unable  to  produce 
even  something  like  a  similar  characteristic  fermentation 
in  several  days  after  having  been  inclosed  in  ice  for  two 
weeks.  The  phenomenon  is  analogous  to  that  which 
Eeimers  (see  p.  130)  observed  concerning  the  bacteria  from 
the  deep  layers  of  the  earth,  and  also  to  that  shown  by  me 

shown  that  "  while  in  some  cases  the  loss  may  reach  as  high  as  90 
per  cent,  it  is  ordinarily  much  less." 

Comparative  analyses  of  white  and  of  transparent  ice,  made  by 
Russell  (loc.  cit.),  show,  as  the  average  of  153  determinations,  that 
the  latter  kind  contained  a  smaller  number  of  bacteria  than  the 
former  ("snow-ice") ;  but  in  several  cases  a  larger  number  of  bac- 
teria per  cc.  was  found  in  clear  transparent  ice  than  was  found  in 
any  sample  of  snow-ice. — W. 


136  MODERN   DAIRY   PRACTICE. 

in  1888  concerning  the  behavior  of  the  lactic  acid  bacteria 
after  repeated  inoculations  in  sugar-free  gelatine.* 

Putrefactive  bacteria  appearing  in  the  ice  also  showed 
a  considerably  diminished  peptonizing  power.  By  inocu- 
lating for  a  long  time  slightly  virulent  bacteria  of  this  kind 
successively  on  new  fermentable  mediums  I  have  again 
been  able  to  awaken  their  fermentative  power  and  gradually 
return  the  normal  virulence  to  the  organisms. 

Uses  of  Purified  Water  in  Factories.  In  some  cases  boiled 
water  had  better  be  applied  in  creamery  and  dairy  work,  and 
in  other  cases  recently  melted  ice-water  had  better  be  ap- 
plied, as  will  be  apparent  from  the  following  examples : 

The  last  rinsing  of  milk  vessels  ought  always  to  be 
made  with  boiling-hot  water.  By  this  we  gain  both  that 
the  vessel  dries  more  rapidly  and  that  the  water  in  evapo- 
rating does  not  leave  behind  living  bacteria.  The  same  is 
true  in  rinsing  the  churn,  butter-worker,  and  all  other 
utensils  coming  in  direct  contact  with  milk,  cream,  or 
butter. 

Before  the  cream  is  poured  into  the  churn  the  walls  of 
the  latter  ought  to  be  given  the  temperature  proper  for 
churning  by  the  application  of  recently-melted  ice-water. 
When  the  butter,  as  is  often  the  case,  especially  in  making 
"  Paris  butter,"  is  to  be  washed  in  the  churn  we  ought 
generally  to  use  water  of  comparatively  low  temperature, 
according  to  the  experience  gained  at  several  creameries. 
40°  F.  (4°  C.)  is  considered  the  best  temperature  at  many 
places.  Water  containing  pieces  of  ice  is  well  adapted 
to  this  purpose;  the  pieces  of  ice  ought  not,  of  course,  to 
go  into  the  churn. 

*  "  See  Saprofyta  mikro-orga'nismer  i  komjolk,"  pp.  36-42. 


CHAPTER  V. 
MILK  FOR  CITY  CONSUMPTION. 

IT  does  not  come  within  the  range  of  this  work  to  treat 
this  subject  exhaustively.  I  cannot  refrain,  however,  from 
referring  to  certain  phases  of  it,  since  we  may  then  learn 
the  manner  in  which  milk  is  usually  kept  when  intended 
for  direct  consumption,  and  will  have  an  opportunity  to  ex- 
plain the  causes  of  some  difficulties  which  city  people  meet 
in  their  efforts  to  keep  milk  sweet.  The  treatment  of  the 
milk  before  it  comes  to  the  household  plays,  of  course,  an  im- 
portant part  as  regards  the  question  of  its  keeping  quality, 
as  may  be  inferred  from  the  preceding.  I  want  to  impress 
on  housekeepers,  first  of  all,  that  they  must  not  buy  milk 
blindly :  they  themselves  should  investigate  the  conditions 
on  the  farm  where  the  milk  used  in  their  household  is 
produced.  This  is  easily  done  where  the  milk  is  obtained 
from  a  farm  in  the  town  where  they  reside;  but  even  if  the 
milk  comes  from  the  country  they  should  not  neglect  to 
inform  themselves  concerning  the  conditions  of  cleanliness 
in  the  stable.  This  is  above  all  necessary  to  insure  one's 
self  against  the  spreading  of  contagion  through  the  milk,  a 
danger  which  has  not  been  treated  in  this  book,  but  which 
cannot  be  disregarded.  Such  an  investigation  is  the  only 
way  in  which  a  housewife  can  protect  herself  against  ob- 
taining unclean  milk.  If  the  milk-producers  were  under 

137 


138  MODERN    DAIRY   PRACTICE. 

the  special  supervision  of  the  consumers  it  would  act 
highly  beneficially  and  educationally  for  the  whole  milk 
business;  with  their  naturally  higher  sense  of  cleanliness 
the  housekeepers  would  be  able  to  call  the  attention  of  the 
milkman  to  many  conditions  deleterious  to  the  cleanliness 
of  the  milk  that  may  not  have  come  under  his  observation. 

Their  influence  is  especially  necessary  for  starting  a 
reform  regarding  stables  situated  in  small  towns;  accord- 
ing to  my  observations  these  are  generally  almost  below 
criticism,  as  far  as  cleanliness  is  concerned.  My  investi- 
gations of  the  milk  from  different  city  stables  have  further 
verified  this  fact. 

On  approaching  such  a  stable  we  find  stinking  manure 
and  other  filthiness  outside  the  door,  and  the  air  in  the 
stable  and  around  it  as  a  result  becomes  intolerable,  espe- 
cially on  warm  days.  The  stable  air  is  often  so  bitter  and 
sharp  that  it  makes  the  eyes  of  the  visitors  smart,  and 
when  the  door  is  closed  complete  Egyptian  darkness  reigns. 
This  darkness  has  a  bad  influence  on  the  keeping  quality 
and  paiatability  of  the  milk,  as  is  plain  to  every  one  who 
has  studied  the  preceding  chapters.  Still  more  shocking 
than  the  accommodations  are  the  animals  in  such  a  stable. 
They  are  usually  dirty  and  unbrushed  from  horns  to  tail, 
and  manure  particles  may  be  seen  all  over  their  bodies 
We  readily  see  how  these  conditions  will  influence  the  milk 
produced  by  the  cows. 

The  filthy  condition  of  many  of  these  stables  arise  first 
of  all,  I  suppose,  from  the  fact  that  they  usually  are  very 
narrow,  dark,  and  poorly  arranged,  but  other  factors  also 
contribute  to  the  result;  litter  is  expensive  in  cities  and 
towns,  and  the  cows  are  fed  large  quantities  of  concen- 
trated feeds,  brewers'  grains,  distillers'  slump,  etc.,  which 


MILK  FOE  CITY  CONSUMPTION.  139 

produce  a  very  soft  and  stinking  manure.*  It  is  expen- 
sive to  preserve  cleanliness  under  such  conditions;  but,  on 
the  other  hand,  such  farms  pay  better  than  those  in  the 
country,  and  their  owners  ought  therefore  to  be  willing 
to  go  to  somewhat  greater  expense.  It  is  deplorable,  how- 
ever, that  in  most  cases  they  do  not  even  pretend  to  keep 
their  cows  clean. 

We  saw  before  (see  page  87)  that  a  milk  examined 
half  an  hour  after  milking  on  three  consecutive  days  con- 
tained the  following  number  of  bacteria  per  cubic  centi- 
meter: 730,000,  560,000,  and  780,000.  This  milk  came 
from  a  village  cow-stable  of  the  kind  just  described;  its 
taste  was,  strange  to  say,  very  good,  and  it  gave  the  impres- 
sion of  being  unusually  rich,  But  it  very  soon  spoiled; 
although  kept  011  a  window-sill  at  a  temperature  of  about 
45°  F.,  it  coagulated  slightly  and  turned  "  off  flavor"  after 
only  ten  hours.  The  examination  spoken  of  took  place 
in  April.  Analyses  of  milk  from  similar  farms  gave  also 
bad  results,  although  the  bacteria  content  was  not  as 
large  as  in  the  case  mentioned. 

The  explanation  that  such  milk  can  be  used  in  house- 
holds in  spite  of  all  it  has  gone  through  lies  in  the  fact 
that  it  is  rapidly  consumed.  It  is  delivered  to  the  cus- 
tomers as  soon  as  it  is  milked,  and  often  consumed  a  couple 
of  hours  afterwards.  _  T 

*  Soxhlet  states  (Munch,  med.  Woch.,  1891,  No.  19)  that  feeding 
stuffs  causing  frequent  evacuations  of  a  thin  dung  favor  the  con- 
tamination of  the  milk,  since  they  make  it  more  difficult  to  keep  the 
cows  clean  ;  to  these  belong  sour  distillers'  slump,  root  leaves,  dif- 
fusion chips,  etc.  The  potato  bacillus  present  in  distillers'  slump 
furthermore  makes  the  milk  liable  to  abnormal  fermentations ;  hay- 
dust  contaminates  the  milk  in  a  similar  way.  See  also  Auerbach, 
Berl.  klin.  Wochenschr.,  1893,  No.  14.— W. 


140  MODERN   DAIRY   PRACTICE. 

Coming  now  to  the  milk  furnished  by  farms  in  the 
country,  we  find  of  course  better  conditions  in  many  re- 
spects. We  have  here  two  different  kinds  of  stables — 
primitive  and  comparatively  modern  ones.  The  former 
remind  one  in  the  main  of  the  village  stables  just  de- 
scribed, although  they  are  a  good  deal  better.  The  build- 
ing of  the  stable,  the  lack  of  windows,  and  some  other 
conditions  are  similar  in  the  two  cases,  but  the  cows  in 
poor  country  stables  are  generally  much  cleaner  than  those 
in  town  stables.  Litter  is  more  plentiful  in  the  country, 
and  the  feeding  of  the  cows  is  seldom  so  intense  as  in  the 
city.  This  superiority  of  old  country  stables  is,  however, 
only  relative ;  if  we  compare  them  with  the  modern  stables 
in  the  country  the  judgment  would  be  entirely  different. 

I  have  only  had  occasion  to  analyze  milk  from  such 
farms  a  few  times.  As  already  stated,  a  sample  of  milk 
produced  in  such  a  stable  was  very  strongly  infected  with 
bacteria  five  hours  after  milking. 

"We  meet  with  better  conditions  and  better  results  in 
examining  the  country  farms  equipped  and  conducted  in 
a  modern  manner.  Conditions  are  also  here  found,  how- 
ever, which  need  improvement,  as  may  be  inferred  from 
the  description  in  Chapter  II. 

The  milk  furnished  to  city  households  is  not  consumed 
until  after  a  shorter  or  longer  transportation.  As  the  milk 
becomes  more  or  less  contaminated  in  every  stable,  it  must 
be  strained  and  cooled  immediately  after  the  milking.  If 
the  milk  is  properly  cooled  before  the  transportation  it 
will  not  be  necessary  to  cool  it  during  the  same,  provided 
the  distance  is  not  too  great:  it  need  then  only  be  pro- 
tected from  being  warmed  which  may  be  effected  by  plac- 
ing the  milk-cans  in  double-walled  boxes,  the  walls  of 


MILK   FOR   CITY   CONSUMPTION.  141 

which  have  been  packed  with  dry  shavings,  saw-dust,  or 
similar  material. 

The  milk  should  of  course  be  delivered  to  the  consum- 
ers as  soon  as  possible  after  having  been  drawn;  but  in 
many  cases  it  is  impossible  to  so  arrange  matters  as  to 
bring  it  directly  into  their  hands,  and  it  is  left  at  some 
"milk-depot"  in  the  city. 

Milk-depots. — Fortunately  the  milk-depots  in  our  larger 
cities,  thanks  to  the  vigilance  of  our  health  officers,  have 
of  late  improved  in  many  ways.  Some  features,  however, 
need  further  examination  and  subsequent  change.  A  milk- 
depot  ought  to  be  as  neat,  light,  and  clean  as  a  creamery, 
and  should  have  many  of  the  facilities  of  the  latter  at  its 
disposal.  The  salesroom  should  be  arranged  so  that  the 
customers  never  need  come  near  the  milk-room.  The 
milk  is  to  be  cooled  to  prevent  any  bacterial  development 
worth  mentioning  from  taking  place  in  the  same.  The 
temperature  of  the  milk  ought  never  to  exceed  45°  F. 
Sour  and  sweet  milk  must  not  be  kept  in  the  same  room; 
nor  should  cheese  or  other  articles  of  food  be  kept  to- 
gether with  sweet  milk.  If  some  milk  is  spilled  it  should 
immediately  be  wiped  up.  As  regards  the  floor,  the  same 
holds  true  in  the  main  as  already  stated  concerning  cream- 
ery-floors. Neatness  must  be  everywhere.  The  supply 
of  ice  should  not  be  scant  or  even  entirely  lacking,  as 
unfortunately  is  no  unfrequent  occurrence  in  many  milk- 
depots. 

Care  of  Milk  in  the  Household.— When  the  milk  has 
reached  a  city  household  it  seems  to  be  a  general  supposi- 
tion that  it  requires  no  further  care.  It  is  argued  that, 
if  it  is  good  it  will  keep;  if  it  is  poor  and  sours  soon  we 
change  milkmen.  This  reasoning  is,  however,  unjust  to 


142  MODERN   DAIRY    PRACTICE. 

both  parties  concerned.  It  is  fortunate  that  the  milk  in 
cities  is  consumed  so  soon,  for  otherwise  the  injurious  re- 
sults of  this  careless  treatment  would  oftener  show  them- 
selves. 

Milk  kept  in  the  dark  in  covered  and  unventilated 
cupboards  often  does  not  sour,  but  assumes  an  insipid,  sick- 
ening, or  bitter  taste,  and  shows  distinct  signs  of  putrefac- 
tive fermentations  on  standing  for  a  longer  time.  This 
led  me  to  investigate  why  especially  putrefactive  bacteria 
gain  the  upper  hand  in  such  milk;  and  I  found  that  the 
conditions  of  light  are  first  of  all  the  causes  of  it. 

Although  bacteria,  generally  speaking,  develop  best  in 
the  dark,  we  observe  in  some  a  greater  dislike  to  light  than 
in  others.  Bacteria  of  milk  may  be  separated  in  two  dis- 
tinct groups,  according  to  their  behavior  in  this  respect. 

1.  Those  that  can  stand  daylight  without  injury. 

2.  Those  that  develop  only  with  difficulty  in  daylight. 
The  lactic-acid  bacteria  belong  to  the  former  group,  and 
the  great  majority  of  the  putrefactive  bacteria  and  the 
butyric-acid  bacteria  to  the  latter. 

If  the  milk-room  is  airy  and  well  ventilated  as  well  as 
light  and  clean,  we  can  conclude  with  a  great  deal  of  cer- 
tainty, provided  the  milk  has  been  properly  handled  at  the 
farm,  first,  that  a  comparatively  small  number  of  bacteria 
is  found  in  it,  and  second,  that  putrefactive  bacteria  are  in 
the  minority.  The  lactic- acid  bacteria,  which  are  practi- 
cally everywhere,  will  then  thrive  best,  and  keep  the  putre- 
factive bacteria  in  check — at  least  as  long  as  the  nutritive 
conditions  are  favorable. 

Sometimes  a  slight  acidity  in  the  milk  can  also  be  dis- 
covered by  chemical  reactions:  this  has  arisen  partly 
through  the  lactic-acid  bacteria,  which  owing  to  their 


MILK   FOR  CITY   CONSUMPTION.  143 

unusual  powers  of  resistance  can  if  only  in  a  small  degree, 
develop  their  specific  qualities,  and  partly  because  bacteria 
forming  other  acids  in  the  milk  have  been  able  to  de- 
velop. Even  some  moulds  which  do  not  seem  to  have  any 
special  liking  for  the  light  play  a  certain  part  in  these 
changes  of  the  milk. 

Considering  what  has  been  said,  we  cannot  be  surprised 
that  the  putrefactive  bacteria  gain  the  upper  hand  in  milk 
kept  in  dark,  small,  city  cellars  or  pantries. 

One  of  the  reasons  why  milk  spoils  so  soon  in  old 
and  poorly  ventilated  milk-rooms  and  depots  is,  that  the 
infection  is  allowed  to  become  more  intense  and  thorough 
with  every  day,  as  the  rooms  are  not  thoroughly  cleaned 
as  often  as  necessary,  and  are  never  disinfected.  A 
mass  infection  may  therefore  easily  arise  by  the  least 
motion  in  the  room,  and  the  fermentation  in  the  milk  will 
have  a  good  start.  To  this  must  be  added  that  the  tem- 
perature in  such  milk  stores  and  rooms  is  often  very  high. 
Whenever  possible  the  milk  ought  to  be  kept  on  ice;  but 
where  ice  is  not  available  a  too  high  temperature  may  be 
avoided  by  taking  simple  precautions,  as,  for  instance,  by  a 
system  of  ventilation,  by  keeping  the  milk  in  cold  running 
water,  etc. 

One  side  of  the  question  which  cannot  here  be  treated 
fully  is,  that  milk  kept  under  bad  conditions  may  easily 
become  dangerous  to  human  health.  I  shall  here  only 
point  out  that  the  conditions  favoring  the  development  of 
the  bacteria  inimical  to  the  keeping  quality  of  the  milk 
are  also  favorable  to  bacteria  injurious  to  human  health; 
in  fighting  the  former  we  therefore  at  the  same  time  coun- 
teract the  latter. 


CHAPTER  VI. 
STERILIZATION  OF  MILK. 

WE  have  seen  in  the  preceding  chapters  that  it  is  im- 
possible to  obtain  a  product  of  absolute  keeping  quality  by 
our  common  methods  of  handling  the  milk.  It  is  well 
known  that  the  comparatively  poor  keeping  qualities  of  the 
milk  cause  great  difficulties  in  its  handling  and  sale,  and 
efforts  were  already  long  ago  made  to  preserve  the  same  so 
that  it  could  be  better  kept  and  more  easily  handled  in  the 
trade. 

The  simplest  and  most  natural  method  of  preserving 
the  milk  has  already  been  mentioned  several  times,  viz.,  to 
cool  the  milk  sufficiently.  It  is  hardly  practicable  in  the 
trade,  however,  as  it  is  expensive  and  inconvenient  con- 
stantly to  surround  the  milk  with  a  cooling  medium.  This 
is,  nevertheless,  the  only  way  to  preserve  the  milk  without 
its  losing  its  original  qualities;  all  other  methods  cause 
greater  or  smaller  changes  in  the  chemical  composition  of 
the  milk,  its  taste,  appearance,  etc. 

Use  of  Chemicals. — A  method  which  has  long  been  ap- 
plied and  as  long  been  objected  to,  is  to  add  all  kinds  of 
antiseptics  to  the  milk,  salicylic  acid,  boracic  acid,  etc. ; 
these  substances  partly  kill  the  bacteria  themselves  and 
partly  prevent  their  growth;  such  milk  is  often  sold  as 
"  improved  milk/'  but  ought  properly  to  be  called  simply 
adulterated  milk. 

144 


STERILIZATIOK   OF   MILK.  145 

Salicylic  Acid  seems  to  be  the  more  common  chemical 
used  for  preserving  milk.  It  has,  however,  serious  disad- 
vantages. Not  more  than  75  centigrams  per  liter  (about 
10  grains  per  quart)  can  be  applied  before  its  characteristic 
taste  appears  too  strongly.  By  the  application  of  this 
quantity  the  coagulation  of  the  milk  is  retarded,  but  its 
acidity  increases.  It  is  besides  notable  that  the  antiseptic 
influence  of  the  salicylic  acid  appears  best  if  the  milk  is 
kept  at  the  temperature  of  68°  -  77°  F. ;  at  77°  -  104° 
F.,  e.g.,  it  can  hardly  be  observed.  Bersch  states  that  by 
an  addition  of  .1  to  .2  gram  of  salicylic  acid  to  one  liter  of 
recently-drawn  milk  it  may  be  kept  sweet  for  six  days 
longer  than  it  would  if  it  had  not  been  treated  in  this 
way.  As  regards  the  injurious  effect  of  salicylic  acid  on 
human  health,  Kolbe  claimed  to  have  proved  that  this 
acid  is  excreted  very  rapidly  from  the  full-grown  animal 
body,  for  which  reason  no  injurious  accumulation  is  to  be 
feared  in  consuming  an  article  of  food  preserved  with  it; 
but  the  application  of  salicylic  acid  for  the  preservation  of 
milk  is  at  the  present  time  condemned  from  a  hygienic 
point  of  view.  For  this  reason  its  use  is,  e.g.,  in  France 
entirely  prohibited  as  a  preservative  of  food  products. 

Borax  and  loracic  acid  also  are  often  used  for  preserv- 
ing milk.  As  early  as  1883,  however,  Forster  warned 
against  the  application  of  these  substances  for  the  object 
mentioned,  as  even  in  small  doses  they  exert  an  injurious 
influence  on  human  digestive  organs.  Many  other  scien- 
tists, as  Bersch  and  Duclaux,  express  themselves  in  the  same 
direction. 

The  addition  to  the  milk  of  one  or  the  other  substance 
must  always  be  considered  an  adulteration  in  case  the 
consumer  is  not  informed  thereof;  for  such  substances 


14:6  MODERN"   DAIRY   PRACTICE. 

change  the  natural  condition  of  the  milk  and  hide  its  true 
quality.* 

Condensed  Milk. — Another  method  of  preserving  milk, 
to  which  great  hopes  were  attached  in  the  past,  is  to  pre- 
pare condensed  milk  in  hermetically-sealed  tin  cans.  About 
twenty  years  ago  a  large  number  of  expensive  and  mag- 
nificent factories  were  erected  for  this  purpose  in  various 
countries,  but  only  comparatively  few  were  able  to  operate 
for  a  long  time.  The  products  did  not,  as  anticipated,  prove 
of  such  quality  that  it  could  find  a  good  market  anywhere, 
for  which  reason  they  are  now  used  only  in  cases  where 
other  milk  cannot  possibly  be  obtained,  as  for  instance  on 

*  The  indiscriminate  use  of  preservatives  in  food  articles  ought 
to  be  prohibited  by  law ;  this  is  especially  urgent  in  case  of  such 
articles  as  milk  and  other  dairy  products,  which  in  a  large  measure 
enter  into  the  nutrition  of  children  and  convalescents.  Most  Euro- 
pean countries  long  ago  prohibited  the  addition  of  salicylic  and 
boracic  acid,  and  other  antiseptics  in  food,  e.g.,  Germany,  Holland, 
France,  Austria,  Spain,  Italy,  etc.  Mr.  Hehner,  the  President  of  the 
Society  of  Public  Analysts  of  England,  in  the  November  1890  meet- 
ing of  the  Society,  read  a  paper  on  Food  Preservatives  (see  Analyst, 
15  (1890),  p.  221),  in  which  he  forcibly  sums  up  the  question  in  the 
following  paragraph  : 

"  We  should  work  for  the  entire  prohibition  of  all  kinds  of  pre- 
servatives. It  is  time  that  we  went  back  to  natural  food.  I  object 
to  being  physicked  indiscriminately  by  persons  not  qualified  to  ad- 
minister medicine  whilst  I  am  in  health.  I  object  still  more  when  I 
am  ill.  I  object  still  more  strongly  to  have  my  children  physicked 
in  their  milk  or  their  bread  and  butter.  It  is  no  consolation  to  me 
to  know  that  the  physic  is  not  immediately  fatal  or  not  even  violently 
injurious.  The  practice  is  utterly  unjustifiable,  except  from  the 
point  of  view  of  a  dealer  who  wants  to  make  an  extra  profit,  who 
wants  to  palm  off  a  stale  or  ill-prepared  article  upon  the  pub- 


STERILIZATION   OF   MILK.  147 

long  voyages,  in  mining  districts,  etc.  That  this  industry 
at  the  present  is  not  insignificant,  however,  is  apparent 
from  the  fact  that  according  to  official  statistics  not  less  than 
520,000  boxes  were  exported  from  Switzerland  during  1888, 
each  one  containing  forty-eight  one-pound  cans  of  con- 
densed milk.  The  value  of  this  export  article  was  calcu- 
lated to  be  about  half  of  the  value  of  the  export  of  Swiss 
cheese  from  Switzerland. 

Two  different  methods  are  mainly  used  for  the  prepa- 
ration of  condensed  milk.  In  the  older  one  of  these, 
adopted,  e.g.,  in  the  factories  in  Cham  and  Guni  of  the 
Anglo-Swiss  Company,  sugar  is  added  to  the  milk  in  the 
process  of  manufacture.  The  main  features  of  the  method 
are  as  follows :  The  milk  is  repeatedly  heated  to  158°  — 
176°  F.  (70°  -  80°  C.),  and  evaporated  in  vacuum-pans;  40 
to  50  grams  of  cane-sugar  is  then  added  for  every  liter 
(quart)  of  milk.  By  this  method  the  milk  is  sterilized  and 
its  water  content  reduced  to  only  one  fourth  of  the  original 
bulk.  The  final  product  is  a  thick,  syrupy  mass  containing 
all  the  nutritive  components  in  the  milk.  Chemical  analy- 
sis of  this  condensed  milk  shows  its  composition  to  be  23 
to  26  per  cent  water,  6  to  11  per  cent  fat,  8  to  10  per  cent 
casein,  53  to  57  per  cent  sugar,  and  2  to  3  per  cent  ash. 

In  the  other  and  later  method  for  condensing  milk  no 
sugar  is  added,  and  the  product  does  not  therefore  obtain 
the  exceedingly  sweet  taste  which  makes  the  condensed 
milk  prepared  according  to  the  former  method  objection- 
able to  many  persons.  This  method  is  applied,  for  instance, 
at  the  factory  Schuttendobel  near  Hartzhofen  in  the  Bava- 
rian Algauer  Alps,  and  is  described  in  the  following  man- 
ner: 

As  soon  as  received  the  milk  is  cleaned  from  the  dirt 


148  MODERN   DAIRY   PRACTICE. 

contained  in  it  by  means  of  a  separator,  and  is  then  evap- 
orated in  a  vacuum-pan  till  it  contains  37$  of  dry  substance. 
The  condensed  milk  is  filled  into  tin  cans  by  a  special 
measuring  and  filling  apparatus,  and  these  are  then  sol- 
dered and  heated  in  the  sterilizer  under  steam-pressure. 
This  method  seems  to  possess  many  advantages  over  the 
first-mentioned  one.  The  condensed  milk  is  free  from 
milk  dirt,  has  no  disagreeable  sweet  taste,  and  contains 
always  the  same  quantities  of  water;  it  has  therefore 
always  the  same  consistency. 

As  already  stated,  the  condensed  milk  has  not  found 
application  on  the  milk  markets  proper,  although  its  keep- 
ing qualities  have  been  all  that  could  be  wished  for.  Its 
consistency  is  too  different  from  that  of  ordinary  milk,  and 
its  price  has  been  too  high.  The  effort  has  therefore  been 
made  to  preserve  milk  by  sterilization  without  changing 
its  physical  properties.  This  sterilization  of  the  milk  may 
be  effected  in  two  different  ways :  first,  by  filtration,  and 
second,  by  heating.*' 

Sterilization  by  Filtration. — Different  kinds  of  mate- 

*  I  pass  by  the  method  proposed  by  the  Frenchman  Guerin  to  keep 
milk  in  a  frozen  condition.  By  this  method  the  bacteria  are  certainly 
prevented  from  starting  fermentations,  but  the  method  is  not  prac- 
ticable, since  the  milk  undergoes  certain  changes  in  freezing  which 
decrease  its  application.  [Notices  occasionally  appear  in  the  agricul- 
tural press  concerning  the  sale  of  frozen  milk  in  foreign  countries. 
In  the  Danish  Landmandsblade  (vol.  37,  p.  305)  the  following 
item  was  thus  given,  the  correctness  of  which  I  am  not  in  position 
either  to  confirm  or  deny  :  "Frozen  milk  is  an  article  of  food  of  late 
years  introduced  to  an  appreciable  extent  in  France  and  Siberia. 
The  frozen  milk  is  comparatively  easily  transported,  will  keep  for  a 
long  time,  and  when  melted  is  said  to  be  as  palatable  as  fresh  new 
milk."— W.] 


STERILIZATION   OF  MILK. 


149 


rials  have  been  used  for  filter  for  the  purpose  of  steri- 
lizing fluids.  Zahn  used  burnt  clay,  as  did  also  Tiegel  and 
Klebs.  Gypsum  was  used  by  Pasteur  and  others,  porce- 
lain by  Chamberland,  fayence  by  Gautier,  and  asbestos 
cardboard  and  plastic  charcoal  by  Hesse  and  Breyer.  All 
these  substances  easily  take  up  the  mechanical  materials 
suspended  in  a  fluid,  and  thus  also  the  bacteria,  on  the  re- 
moval of  which  the  fluid  will  keep. 

As  Zahn's  experiments  in  my  opinion  in  a  very  simple 
and  plain  manner  illustrate  the  preservation  of  milk  by 
filtration,  I  shall  briefly  describe  his  method  of  procedure. 
Into  a  porcelain  tube  glazed  on  the  outside  he  fitted  tightly 
a  rubber  stopper,  in  which  a  tube  connected  with  an  aspi- 
rator was  placed.  The  apparatus  was  then  sterilized. 
When  cold,  it  was  lowered  into  the  milk 
and  the  aspirator  opened.  By  means  of 
this  simple  apparatus,  shown  in  the  accom- 
panying illustration,  Zahn  succeeded  in 
sterilizing  the  milk.  (Fig.  25). 

Several  different  kinds  of  apparatus  for 
sterilizing  fluids  by  filtration  are  made  at 
the  present  time;  none  of  these  are  fully 
practical,  however;  the  most  promising 
ones  are  the  porcelain  filters  of  Chamber- 
land's  mentioned  in  the  preceding,  which 
act  continuously  and  regularly. 

It  is  easy  to  sterilize  milk  in  this  manner,  but  unfortu- 
nately it  is  changed  also  in  other  ways  by  this  method. 
Duclaux  has  thus  shown  through  lengthy  experiments 
that  not  less  than  nine  tenths  of  the  albumen  content 
of  the  milk  remains  in  the  filter.  The  albuminoids  are 
not  really  dissolved  in  the  milk,  but  appear  in  it  in  an 


FIG.  25. 


150  MODERN   DAIRY   PRACTICE. 

exceedingly  fine,  suspended  condition.  The  difference 
between  the  milk  and  the  fluid  passing  the  filter  is  so  great 
that  the  latter  hardly  can  be  called  milk.  Its  most  nutri- 
tious constituent  is  gone.  By  this  filtration  the  steriliza- 
tion of  the  milk  is  therefore  obtained  at  the  expense  of  its 
nutritive  value. 

In  the  experiments  which  I  have  made  in  filtering  milk 
by  means  of  Chamberland's  filter  the  fat  globules  of  the 
milk  have  furthermore  often  caused  difficulties,  as  they 
will  not  easily  go  through  the  filter  at  a  rather  low 
temperature,  and  usually  clog  its  inner  portion  so  that 
the  cleaning  is  very  difficult.  The  same  must,  of  course, 
also  be  the  case  when  other  methods  of  filtration  are 
applied.  The  method  of  sterilizing  the  milk  through 
filtration  must  then,  at  least* in  its  present  phase,  be  re- 
jected.* 

Sterilization  of  Milk  by  Heating. — Before  entering  on 
this  subject  it  may  be  proper  to  state  briefly  the  chemical 
changes  which  milk  undergoes  in  heating.  These  changes 
are  not  noticed  until  the  heating  rises  to  about  185° 
F.  (85°  C.),  when  a  small  separation  of  albumen  may  be 
observed  as  a  white  precipitate.  Small  quantities  of 
casein  also  seem  to  separate  at  the  same  time.  If  the  tem- 
perature is  increased  above  185°,  the  albumen  will  be  pre- 
cipitated more  heavily,  and  the  power  of  coagulation  of 
the  casein  will  be  decreased.  A.  Mayer  states  that  this 
power  is  decreased  even  at  167°  F.  (75°  C.).  If,  however, 
the  temperature  of  the  milk  is  slowly  raised  to  167°  F.,  yes, 

*  While  the  apparatus  mentioned  are  of  no  practical  value  for 
sterilization  of  milk,  they  serve  in  an  excellent  manner  as  water-fil- 
ters, and  are  extensively  used  as  such,  especially  in  larger  cities,  or 
where  the  drinking-water  available  is  not  above  suspicion. — W. 


STERILIZATION    OF   MILK.  151 

even  to  212°  F.,  then  cooled  to  about  86°  F.,  and  good 
rennet  added  in  larger  quantities  than  usual,  distinct 
symptoms  of  coagulation  will  appear,  although  much  slower 
than  ordinarily.  Not  only  are  the  albuminoids  of  the  milk 
changed  by  a  stronger  heating,  but  the  milk  sugar  also 
shows  the  influence  of  the  heat.  If  a  temperature  of  185° 
to  200°  F.  acts  on  the  milk  for  some  time  or  at  intervals, 
it  will  be  easily  noticed  that  it  assumes  a  brown  coloration ; 
this  occurs  through  a  formation  of  caramel  in  the  milk,  its 
milk  sugar  being  partly  decomposed. 

If  the  heating  is  carried  farther,  the  symptoms  men- 
tioned become  still  more  noticeable,  and  at  the  same  time 
the  cooked  taste,  which  was  only  slight  by  heating  to  about 
167°  F.,  becomes  more  pronounced.  At  266°-300°  F.  a 
coagulation  of  casein  takes  place,  according  to  Hammar- 
sten,  in  a  manner  chemically  identical  with  the  coagula- 
tion through  the  addition  of  rennet. 

The  sterilization  through  heating  is  in  practice  con- 
ducted in  two  ways:  1,  ty  foiling  under  pressure,  and  2, 
ty  ordinary  foiling. 

The  ormer  method  was  introduced  into  practice  by 
Nageli,  who,  at  the  Dairy  Exposition  in  Berlin  in  1879, 
published  his  experiences  with  the  same.  As  the  foremost 
spokesman  of  this  method  in  practice,  E.  Scherif,  in  Wen- 
disch  Buchholtz  (Berlin),  has  made  himself  known,  and 
ScherfP  s  milk  has  of  late  often  been  spoken  of.  Ac- 
cording to  his  method  of  procedure  the  newly-drawn  milk 
is  poured  into  glass  bottles,  which  are  stoppered,  and  then 
heated  under  pressure  at  248°  F.  (120°  C.)  for  one  to  two 
hours.  This  method  is  old,  and  has  long  be_en_known  in 
science.  The  new  in  Scherff  s  meth 


152  MODERN   DAIRY   PRACTICE. 

ventor  has  patented  in  Germany,  lies  in  the  peculiar 
method  of  closing  the  bottles. 

Scherff  s  milk  will  keep  beyond  question;  both  bacteria 
and  their  spores  are  killed  by  this  treatment.  But  even 
by  the  application  of  this  method  the  milk  undergoes  all 
kinds  of  changes,  as  is  natural  at  such  a  high  temperature, 
so  that  its  usefulness  is  greatly  impaired.  The  milk 
assumes  a  cooked  taste,  which  often  approaches  that  of 
burnt  milk:  and  the  color  is  often  brownish,  showing 
that  a  caramel  formation  has  taken  place.  Munk  even 
found  that  Scherff's  milk  had  to  be  mixed  with  four 
times  the  customary  quantity  of  rennet  to  effect  a  coagu- 
lation, and  that  this  process  took  place  more  slowly  than 
usual  in  spite  of  this  liberal  addition  of  rennet. 

The  other  method  of  sterilizing  milk  by  heating  is  to 
boil  it  at  ordinary  pressure.  Experiments  were  made 
in  sterilizing  milk  by  heating  to  212°  F.  for  two  hours, 
but  this  method  proved  unsatisfactory,  as  no  reliable 
sterilization  was  obtained.  It  has  been  found  that  spores 
of  several  bacteria  will  survive  this  process.  The  spores  of 
the  hay  bacillus,  which,  as  before  mentioned,  is  often  found 
in  milk,  are  not  killed  by  such  a  heating  continued  even 
for  six  hours.  The  spores  of  the  butyric-acid  bacillus  are 
so  tenacious  of  life  that  they  survive  boiling  from  one  to 
two  hours.  The  same  is  true  for  Duclaux's  Tyrothrix 
tennis. 

This  temperature  having  proved  insufficient,  experi- 
ments were  made  by  heating  the  milk  to  a  higher  degree. 
Pasteur  found  that  a  single  heating  to  225°-227°  F.  is  ordi- 
narily sufficient  to  sterilize  the  milk.  Other  investigators 
again  state  that  it  is  necessary  to  heat  the  milk  230°-239°  F. 
to  make  certain  of  complete  sterilization.  Other  difficul- 


STERILIZATION   OF   MILK.  153 

ties  came  in  with  this  strong  heating,  however.  The  milk 
assumed  a  brown  color  and  acquired  a  burned  or  boiled 
taste,  whicl  was  generally  objected  to  by  consumers. 

Such  milk  cannot  be  used  for  baby-feeding.  It  is 
furthermore  very  expensive,  and  difficult  to  arrange  for 
this  heating  on  a  large  scale.  It  can  only  be  done  by 
means  of  a  so-called  autoclave,  or  by  the  application  of  salt 
solutions.  It  therefore  proved  impossible  in  many  cases 
to  apply  high  temperatures  for  the  sterilization  of  milk. 

Through  Tyndall's  and  Gay-Lussac's  investigations  we 
have  learned,  however,  that  sterility  may  also  be  obtained 
in  liquids  by  application  of  lower  heating  by  the  so-called 
intermittent  sterilization,  which  was  already  spoken  of 
in  the  Introduction  (see  p.  15).  Hueppe  seems  to  have 
been  the  first  one  to  apply  this  method  for  sterilization  of 
milk.  He  stated  that  it  was  only  necessary  to  apply  a 
temperature  of  167°  F.  (75°  C.)  for  half  an  hour  for 
five  consecutive  days.  It  has  been  found,  however,  that 
this  method  is  not  always  reliable.  Only  where  the  re- 
sults obtained  can  be  controlled,  as  in  laboratories  by 
testing  in  an  incubator  or  similar  apparatus,  can  they  be 
relied  on.  In  my  experiments,  cultures  of  certain  species 
of  potato  bacilli  in  milk  have  stood  such  a  treatment  with- 
out appreciably  losing  their  vitality.  We  know  bacteria 
which  develop  well  at  about  158°  F., — a  fact  sufficient  to 
shake  our  faith  in  the  reliability  of  a  method  of  steriliza- 
tion of  the  kind  mentioned.  This  also  shows  the  reason 
why  different  scientists  have  come  to  such  different  re- 
sults in  their  investigations  of  this  subject.  One  states 
that  milk  may  be  sterilized  perfectly  by  repeated  heating 
to  167°  F.,  and  another  that  a  considerably  higher  tem- 
perature must  be  applied.  The  difference  of  results  comes, 
of  course,  from  the  fact  that  different  bacteria  were  found 


154  MODERN   DAIRY   PRACTICE. 

in  the  samples  of  milk  investigated.  Hueppe  has  later  pre- 
scribed that  the  intermittent  sterilization  of  milk  takes 
place  best  by  exposing  it  to  live  steam  at  212°  F.  during 
the  first  day  for  an  hour,  and  during  each  of  the  follow- 
ing two  or  three  days  for  twenty  to  thirty  minutes.  As 
already  stated,  a  separation  of  the  albumen  of  milk  takes 
place  at  this  temperature,  its  behavior  toward  rennet  is 
changed,  and  an  almost  imperceptible  change  in  some  of 
the  milk-sugar  takes  place. 

The  intermittent  sterilization  applied  in  laboratories 
has  also  been  introduced  in  practice  for  the  preservation 
of  milk  by  the  Norwegian  Chr.  Gerhard  Dahl  of  Dram- 
men,  who  succeeded  so  well  in  this  that  at  the  last  Paris 
Exposition  he  could  show  milk  several  years'  old  prepared  at 
his  factory.  This  milk  is  said  to  have  been  very  palatable,  al- 
though it  possessed  a  distinctly  cooked  taste,  which,  however, 
according  to  a  statement  made  by  a  visitor  at  the  Exposition, 
was  no  more  pronounced  than  that  of  ordinary  boiled  milk. 

Dahl  describes  his  method  in  the  following  manner  in 
the  letters-patent  granted  in  Germany  November  14,  1886 
(quoted  from  Molkerei-Zeitung] : 

The  method  of  condensing  the  milk  consists  in  (1)  cool- 
ing the  newly-drawn  milk  to  50°-64°  F.  (10°-15°  C.);  (2) 
filling  the  milk  into  cans;  (3)  air-tight  stoppering;  (4)  heat- 
ing of  the  cans  to  about  158°  F.  (70°  C.)  for  about  one  and 
three  quarters  of  an  hour;  (5)  cooling  to  104°  F.  (40°  C.)  for 
one  and  three  quarter  hours,  and  then  (6)  rapid  heating  of  the 
milk  to  158°  F.  (70°  C.);  (7)  repetition  of  these  three  pro- 
cesses— heating,  cooling,  heating — with  about  one-half-hour 
intervals;  (8)  a  final  heating  for  one  half -hour  to  176°-212° 
F.  (80°-100°  C.);  and  finally  (9)  cooling  to  59°  F.  (15°  C.). 

Good  results  can  doubtless,  as  a  rule,  be  obtained  by 
this  or  a  similar  method  of  procedure.  Difficulties  of  all 


STERILIZATION   OF  MILK.  155 

kinds  have,  however,  arisen  also  here.  First  of  all,  per- 
fectly satisfactory  condensing-cans  have  not  been  obtained. 
Those  applied  by  Dahl  were  of  sheet  iron,  and  were  made 
air-tight  by  soldering  the  cover  on.  The  weak  points  of 
these  cans  are,  that  they  can  only  be  used  once — when  the 
can  is  once  opened  the  milk  will  spoil  comparatively  soon ; 
and  they  are,  rather  expensive  to  be  used  for  so  cheap  an 
article  as  milk.  Glass  bottles  would  be  far  better  in  many 
respects,  but  they  are  so  easily  broken  during  the  heating 
as  to  greatly  increase  the  expense  of  the  sterilization. 

Like  ScherfPs  method,  that  of  Dahl  has  been  modified 
in  many  ways  without  any  really  practical  and  reliable 
method  for  the  preservation  of  the  milk  having,  to  my 
knowledge,  yet  been  found.  The  difficulties  which  have 
not  yet  been  overcome  are  partly  that  the  proper  preserv- 
ing cans  come  too  dear,  partly  that  the  milk  is  not  com- 
pletely sterile,  or  else  must  be  heated  so  high  that  it 
assumes  a  disagreeable  cooked  taste,  and  is  changed  in 
quality  and  appearance.  Different  apparatus  have  been 
constructed,  and  preserving-cans  of  the  most  varying  kinds 
have  been  invented  and  improved.  [Among  German 
methods  which  have  given  satisfactory  results  in  practice 
may  be  mentioned  that  of  Neuhaus,  Gronwald,  and  Oehl- 
mann  (see  Weigmann,  "  Milchconservirung,"  1893,  p.  47). 
In  the  investigation  made  by  Petri  and  Massen  in  regard 
to  milk  sterilized  by  this  method  they  found,  however, 
among  the  six  hundred  bottles  examined  "  a  large  num- 
ber of  bottles"  containing  living  bacteria.*]  Patents  in 
large  numbers  have  been  granted  in  different  countries, 
and  each  inventor  has  claimed  with  confidence  that  the 
problem  has  been  solved,  and  that  his  apparatus  and 
method  may  be  successfully  applied  anywhere. 

The  bacteria  found  in  milk  during  different  seasons 
*  Author's  addition  to  American  translation. 


156  MODERN   DAIRY   PRACTICE. 

and  under  different  conditions  vary  so  greatly  that  the 
sterilization  of  milk  on  a  large  scale  must  always  remain 
a  difficult  problem.  In  my  opinion  we  ought  to  begin 
with  reforms  in  the  cow-stable,  and  better  milk,  contain- 
ing fewer  bacteria,  than  that  now  generally  available, 
should  be  supplied.  Some  milk  is  difficult  to  sterilize  and 
other  milk  is  easily  made  germ-free.  Sometimes  this  may 
be  attained  by  a  single  heating  of  three  fourths  of  an 
hour;  sometimes,  again,  the  operation  has  to  be  repeated 
for  three  or  four  days.  According  to  my  investigations 
this  depends,  without  doubt,  on  the  treatment  which  the 
milk  receives  on  the  farm.  The  milk  from  the  same 
farms  also  shows  a  certain  regularity  as  regards  the  diffi- 
culties met  with  in  its  sterilization.* 

As  long  as  the  question  of  the  sterilization  of  the  milk 
by  heating  for  practical  purposes  is  at  its  present  stage  we 
ought,  however,  in  my  opinion,  to  receive  with  great  re- 
serve claims  that  some  experimenters  have  succeeded  in 
solving  the  problem. 

[Since  the  preceding  account  of  the  sterilization  of 
milk  was  written  (1891),  the  question  has  not  received  any 
further  light.  An  excellent  exposition  of  the  subject  is 
given  by  H.  Weigmann  in  his  small  work,  already  referred 
to,  on  "  Methods  of  Preservation  of  Milk  "  ("  Die  Methoden 
der  Milchconservirung,"  Bremen,  1893,  176  pp.),  to  which 
the  reader  interested  in  the  subject  is  referred.  The  book 
is  especially  complete  as  regards  descriptions  of  different 
kinds  of  apparatus  and  methods  proposed  for  the  steriliza- 
tion and  pasteurization  of  milk.f] 

*The  preparation  of  absolutely  germ-free  milk  is  more  easily 
accomplished  the  purer  and  fresher  the  milk  used, — a  fact  which 
is  of  the  greatest  importance  to  milk-condensing  factories  as  well  as 
to  physicians  and  persons  using  sterilized  or  even  pasteurized  milk. 
See  Weigmann,  "  Milchconservirung,"  1893,  p.  51.— W. 

•f  Author's  addition  to  American  translation. 


CHAPTER  VII. 
PASTEURIZATION  OF  MILK. 

ONE  phase,  and  perhaps  the  most  important  one  in  the 
sterilization  of  milk,  has  not  yet  been  touched  upon,  viz., 
that  at  the  same  time  as  the  milk  has  been  made  to  keep 
it  has  also  been  improved  from  a  hygienic  point  of  view. 
Milk  is  an  exceptionally  good  nutritive  medium  for  most 
bacteria;  we  know  that  it  has  been  the  means,  although 
comparatively  seldom,  of  spreading  various  dangerous 
diseases,  as  tuberculosis,  diphtheria,  typhoid  and  scarlet 
fever.  These  are  all  infectious  diseases  caused  by  different 
kinds  of  bacteria.  The  bacteria  thrive  well  in  milk; 
once  there  and  with  the  person  consuming  the  milk  liable 
to  contagion,  infection  and  disease  will  easily  be  the  result. 

The  pathogenic  bacteria  existing  in  milk  are  fortu- 
nately all  killed  rapidly  at  a  comparatively  low  tempera- 
ture. Special  investigations  have  shown  that  they  can 
hardly  stand  a  heating  up  to  167°-185°  F.  (75°-85°  C.).* 
It  is  therefore  not  necessary  to  obtain  complete  sterility 
in  the  milk  to  guard  against  infectious  bacteria. 

As  regards  the  other  bacteria  in  milk,  I  want  to  call  at- 
tention to  a  point  suggested  by  my  heating  experiments 
with  milk  containing  bacteria  of  different  kinds.  If  the 
heating  was  continued  to  about  167°  F.  (75°  C.)  it  was 
shown  by  subsequent  bacteriological  examinations  that  the 

157 


158  MODERN   DAIRY    PRACTICE. 

lactic-acid  bacteria  proper  had  disappeared  or  else  were 
considerably  reduced  in  number,  and  that  even  putrefac- 
tive bacteria  had  decreased  in  number,  although  not  as 
much  as  the  former.  This  change  in  the  bacterial  content 
was  so  striking  that  it  could  be  observed  by  a  mere  micro- 
scopic examination,  and  showed  that  the  pure  bacilli  forms 
had  entirely  gained  the  upper  hand  after  the  heating.  I 
am  not  in  possession  of  sufficient  medical  knowledge  to 
state  the  hygienic  importance  of  the  disappearance  of  the 
lactic-acid  bacteria  proper  from  the  milk,  or  at  least  their 
great  diminution,  and  of  the  decrease  in  the  number  of 
bacteria  causing  fermentations  of  the  casein;  but  I  can 
testify  on  the  basis  of  my  investigations  that  this  relation 
plays  an  important  part  in  regard  to  the  keeping  qualities 
of  the  milk,  since  the  lactic-acid  fermentation  usually 
precedes  the  fermentation  processes  caused  by  the  other 
bacteria.f 

The  relative  keeping  qualities  of  the  milk  are  thus 
increased  through  the  disappearance  of  the  lactic-acid 
bacteria. 

A  heating  of  the  milk  to  165°-185°  F.  will  therefore 

*  Bitter  found  that  tubercle  bacilli  were  killed  by  simple  heating 
for  30  minutes  at  154°  F. ;  Forster  (Milchzeitung ,  1894,  p.  84)  ob- 
tained the  same  result  by  heating  for  10  minutes  at  158°  F.,  for  5 
minutes  at  170°  F.,  and  for  1  minute  at  203°  F.  At  lower  tempera- 
tures longer  time  was  required,  viz.,  1  hour  at  140°  F.  and  4  hours 
at  131°  F.  Bang  found  that  a  temperature  of  176°-185°  was  required 
to  kill  tubercle  bacilli ;  see  Part  IV.,  Chapter  I.— W. 

f  Duclaux  mentions  similar  observations  in  the  January  number 
of  Annales  de  I' Institute  Pasteur  for  1891,  and  ascribes  great 
hygienic  importance  to  the  fact  that  the  acid-forming  bacteria  have 
disappeared  in  the  heated  milk,  especially  in  regard  to  the  applica- 
tion of  the  milk  for  baby-feeding. 


PASTEURIZATION   OF   MILK.  159 

not  only  protect  the  consumer  from  infection  of  con- 
tagious bacteria,  but  will  also  appreciably  increase  the 
keeping  quality  of  the  milk.  Such  heating  has  been  called 
pasteurization,  and  is  now  practised  at  a  large  number  of 
creameries.  This  treatment  of  the  milk  is  especially 
necessary  at  large  factories  where  it  is  difficult  to  properly 
supervise  cleanliness,  etc.,  at  the  farms  of  the  patrons. 
The  details  of  pasteurization  will  be  treated  farther  on  in 
this  book. 

There  are,  however,  two  cases  in  which  still  greater 
precautions  are  necessary  for  preventing  infection  from 
milk,  namely,  at  milk  sanatoriums  and  for  baby-feeding. 
In  both  cases  large  quantities  of  milk  are  consumed,  and 
if  this  is  infected  by  malignant  bacteria  infection  may 
easily  arise. 

Milk  for  Sanatoriums. — At  milk  sanatoriums  the  effort 
is  of  course  to  supply  milk  from  as  healthy  cows  as  possi- 
ble and  to  observe  all  possible  neatness  and  cleanliness  in 
the  production  and  handling  of  the  milk  ;  besides  this  an 
obligatory  heating  of  the  milk  is  practised.  This  is  the 
case,  e.g.,  at  the  milk  sanatorium  in  Berlin  under  the 
direction  of  the  well-known  dairy  authority  Benno  Mar- 
tiny;  all  milk  is  there  heated  for  half  an  hour  to  about 
176°  F.  previously  to  consumption. 

Milk  for  Baby-feeding. — The  milk  intended  for  baby- 
feeding  must  also  undergo  a  special  treatment.  *  Babies 

*In  case  of  milk  intended  for  sanatoriums  or  for  baby-feeding, 
special  care  must  be  taken  as  regards  the  system  of  feeding  the 
cows.  Only  well-preserved,  carefully-selected  feed  stuffs  should  be 
given.  Sweet  aromatic  and  well-cured  hay  or  corn  fodder  is  the 
best  coarse  fodder  for  the  purpose.  Corn  silage  must  be  fed  only  in 
small  quantities,  if  at  all ;  always  after  milking,  and  not  to  exceed 
10-15  Ibs.  a  day.  Oat  or  barley  straw  may  also  be  fed  ;  likewise 


160  MODERN   DAIRY   PRACTICE. 

often  consume  cows'  milk  in  large  quantities,  and  their 
systems  possess  less  power  of  resistance  than  that  of  grown 
people,  f  But  even  here  it  may  not  be  necessary  to  strive 
to  reach  complete  sterility,  since  infectious  bacteria  do  not 
appear  to  be  very  resistant  toward  heating.  If  precautions 
are  taken  that  the  milk  is  always  consumed  within  twenty- 
four  hours  at  the  latest  after  the  heating  process,  and  that 
it  is  kept  in  a  cool  place  during  this  time,  it  will  not  be 
infectious  or  undergo  any  injurious  changes. 

The  same  results  may  be  obtained  by  heating  the  milk 
in  an  ordinary  casserole  to  the  boiling  point,  or  even  only 
to  about  158°  F.  It  must  be  remembered,  however,  that 
such  a  heating  does  not  of  course  protect  the  milk  from 

rutabagas  or  carrots  (in  small  quantities).  Of  concentrated  feed  stuffs, 
the  cereals  or  the  flour-mill  refuse-products  may  safely  be  fed,  but  not 
pea-meal,  bean  meal,  or  any  other  legumes.  Malt-sprouts,  linseed- 
meal,  palm-nut  meal,  cocoanut-meal,  etc.,  may  be  fed  sparingly — all 
but  the  first-mentioned  not  to  exceed  one  pound  of  each  feed  a  day 
per  head.  No  fermented  or  rancid  feed  should  be  given  (except 
silage,  with  the  proviso  mentioned),  and  no  slump  feed,  brewers' 
grains,  etc.  The  milk  from  fresh  cows  should  not  be  used  for  this 
purpose  until  the  eighth  day  after  calving,  and  never  under  any  con- 
dition unless  the  cows  are  perfectly  healthy  and  give  milk  fully 
normal  according  to  both  taste,  smell,  and  appearance.— W. 

fMunkand  Uffelmann(intheir  "Ernahrungd.  Menschen,"  1891, 
p.  294)  state  that  "  the  high  germ  content  of  cows'  milk,  especially 
of  fermentative  forms,  is  doubtless  largely  the  cause  of  its  poorer 
utilization  and  palatability  in  baby-feeding.  Soxhlet  considers  the 
particles  of  dung  very  frequently  present  in  cows'  milk  the  main 
carriers  of  these  bacteria;  and  he  is  doubtless  right.  Experience 
teaches  us  at  any  rate  that  feeding  babies  with  boiled  or  especially 
with  sterilized  milk  gives  far  better  results,  and  causes  a  much 
smaller  number  of  digestive  troubles,  stomach  and  intestinal  catarrhs, 
etc.,  than  does  feeding  with  unboiled  milk." — W. 


PASTEURIZATION   OF   MILK.  161 

renewed  infection  before  it  is  consumed.  To  prevent  this 
infection,  which  is  a  very  important  point  in  case  of  baby- 
feeding,  the  milk  must  be  heated  and  kept  in  a  sterile  and 
carefully  closed  vessel.  Many  different  kinds  of  apparatus 
and  methods  have  been  invented  for  the  treatment  of  milk 
for  this  purpose.  I  shall  here  only  mention  two  methods 
which  may  be  considered  typical.  The  one  was  invented 
by  Dr.  Engli-Sinclair  in  Switzerland;  the  other  by  Dr. 
Soxhlet  in  Germany.  Both  these  methods  are  essentially 
alike :  Engli-Sinclair  works  with  simpler  and  more  primi- 
tive apparatus  than  Soxhlet.  Both  methods  seem  to  give 
perfectly  reliable  results,  although  the  admirers  of  the 
Soxhlet  method  maintain  that  that  alone  fulfils  the  de- 
mands for  an  ideal  milk-sterilizing  apparatus. 

Methods  of  "  Milk-sterilization."  *  —  The  method  of 
Engli-Sinclair  is  as  follows :  In  an  ordinary  porcelain-lined 
iron  casserole  provided  with  a  cover  a  sheet-iron  stand  is 
placed  holding  seven  bottles;  these  will  hold  about  1. 6  liters 
(1|  quarts),  or  about  as  much  milk  as  is  required  for  one 
meal.  The  bottles  are  filled  with  milk  of  the  best  quality, 
which  if  necessary  is  diluted  with  water;  the  bottles  are  at 

*  There  is  some  confusion  in  the  use  of  the  term  sterilization  and 
pasteurization  of  milk  and  milk  products.  Sterilization,  as  we  have 
seen,  implies  absolute  freedom  from  bacteria,  while  pasteurization 
implies  relative  freedom  from  bacteria;  the  former  is  reached  by 
prolonged  heating  at  the  boiling-point  or  higher  temperatures;  the 
latter  by  heating  at  temperatures  from  165°-1S5°  F.  (see  p.  159). 
When  the  methods  to  be  described  in  the  above  were  given  to  the 
world,  it  was  thought  that  the  product  obtained  was  absolutely  germ- 
free,  and  the  process  was  therefore  called  sterilization  of  milk— a  name 
still  applied,  although  according  to  our  present  knowledge  it  is  not 
strictly  correct.  The  methods  are  described  in  the  present  chapter 
because  the  milk  thus  treated  will  act  like  pasteurized  milk,  as  will 
be  apparent  from  the  remarks  of  the  author. — W. 


162  MODERN   DAIRY   PRACTICE. 

once,  without  being  stoppered,  lowered  into  the  casserole, 
which  is  filled  three  fourths  full  of  water.  The  casserole 
is  now  put  over  the  fire,  and  when  the  water  is  boiling  hard 
the  bottles  are  hermetically  sealed  with  rubber  stoppers  and 
the  cover  put  on  the  casserole.  After  half  an  hour  the  cas- 
serole is  taken  away  from  the  fire  and  kept  in  a  cool  place. 
The  bottles  must  cool  in  the  casserole,  as  otherwise  they  are 
liable  to  break.  The  same  bottles  are  used  for  nursing, 
and  a  nipple  carefully  cleaned  and  boiled  each  time  is 
substituted  for  the  cork.  In  this  way  the  different  milk 
portions  are  completely  protected  from  contamination  until 
the  very  moment  they  are  to  be  consumed. 

The  milk  is  treated  exactly  according  to  the  same  prin- 
ciples in  Soxhlet's  method.  The  superiority  of  this  method 
consists  in  the  fact  that  the  apparatus  may  be  used  by  any 
one,  and  is  more  easily  kept  clean,  which  is  a  very  impor- 
tant point.*  As  fresh  milk  as  possible  is  to  be  used,  and 
never  milk  from  a  single  cow — only  mixed  milk.  The  dilu- 
tion of  the  milk  with  water  should  always  take  place  before 
the  boiling.  The  milk  must  be  boiled  for  three  quarters  of 
an  hour.  The  rubber  rings  on  the  bottles  should  not  be  re- 
moved until  the  milk  is  to  be  used.  The  covers  should 
also  be  left  on  the  bottles,  and  the  latter  kept  in  a  cool 
place  after  the  boiling.  When  the  milk  is  to  be  used  it 
should  be  heated  to  body  temperature.  It  is  to  be  remem- 
bered that  the  cold  bottles  must  not  be  placed  in  hot 

*  Soxhlet's  apparatus  with  the  latest  improvements  can  be  ob- 
tained from  the  manufacturer,  Metzeler  &  Co.,  in  Munich,  at  a  price 
of  13  to  16  marks.  A  collection  of  the  most  necessary. pieces  may  be 
obtained  from  the  same  firm  for  10  marks.  The  apparatus  can  doubt- 
less be  obtained  from  American  dealers  in  chemical  glassware  or 
from  wholesale  druggists.— W. 


PASTEURIZATION   OF   MILK.  163 

water;  if  they  do  not  break  immediately  in  such  a  case 
they  will  become  brittle  and  readily  break  in  the  next 
boiling.  Milk  residues  in  the  bottles  should  not  be  saved. 
The  cleaning  of  the  bottles  is  best  effected  as  soon  as  the 
milk  has  been  consumed. 

Ardent  adherents  of  Soxhlet's  method  claim  that  milk 
treated  in  this  way  will  keep  for  three  to  four  days,  and 
advise  that  large  quantities  of  milk  be  sterilized  at  once. 
This  is  doubtless  an  exaggeration.  One  of  the  best  points 
in  the  method  is  in  my  opinion  the  fact  that  small  quanti- 
ties of  milk  may  be  easily  and  cheaply  treated.  If  such 
incompletely  sterilized  milk  is  saved  for  a  longer  time  than, 
e.g.,  twenty-four  hours,  risks  are  doubtless  taken.  If  living 
bacteria  are  found  in  milk  they  will  necessarily  soon  make 
their  presence  known  if  it  is  kept  longer,  and  not  in  a 
cool  place. 

Milk  treated  according  to  Soxhlet's  method  seldom 
becomes  absolutely  sterile.  I  have  made  numerous  ex- 
periments on  this  point  and  have  kept  milk  carefully 
prepared  in  a  Soxhlet  apparatus  at  a  temperature  of  90°  F. 
(32°  0.)  in  an  incubator;  I  have  practically  every  time 
within  forty- eight  hours  been  able  to  verify  in  it  a  large 
number  of  Bacillus-subtilis  forms  and  other  bacteria. 
Soxhlet  warns  against  sterilizing  such  large  quantities  at 
one  time  that  the  milk  has  to  be  kept  long  before  being  used. 
He  holds  that  lactic  acid  is  almost  exclusively  formed  in 
unboiled  milk  kept  at  95°  F.  (35°  C.);  butyric  acid  formed 
at  the  same  time  does  not  make  up  even  4  per  cent  of  the 
total  acidity.  Large  quantities  of  butyric  acid  are,  on  the 
other  hand,  formed  in  samples  of  partially  sterilized  milk — 
at  least  15  per  cent,  on  an  average  30  per  cent,  and  often 
more  than  50  per  cent  of  the  total  acidity.  This  butyric 


164  MODERN   DAIRY    PRACTICE. 

acid  must  be  considered  injurious,  and  it  seems  therefore 
safest  to  prepare  only  as  much  milk  as  will  be  used  during 
twelve  hours.  Soxhlet  has  also  constructed  an  arrange- 
ment for  heating  milk  up  to  the  proper  temperature  imme- 
diately before  consumption. 

In  many  larger  cities,  as,  e.g.,  in  Vienna  (Dr.  Hoch- 
singer),  so-called  milk-sterilizing  stations  have  been  estab- 
lished, where  children's  milk  is  prepared  on  a  large  scale 
according  to  Soxhlet's  method  and  is  sold  in  definite  mixt- 
ures of  milk  and  water  according  to  the  prescription  of 
physicians.  If  careful  supervision  is  given  to  the  station, 
so  that  everything  is  conducted  as  it  ought  to  be,  this  is  an 
excellent  idea,  since  pasteurized  milk  in  this  way  can  be 
had  cheaper  than  if  everybody  pasteurize  milk  for  their 
own  use.  The  Soxhlet  apparatus  is  rather  expensive, 
and  the  cost  is  farther  increased  by  the  frequent  breakage 
of  bottles.  The  cleaning  of  the  apparatus  demands  time 
and  care.  Engli-Sinclair's  method  is  cheaper,  as  before 
mentioned,  but  may  require  greater  care  in  execution  than 
that  of  Soxhlet. 

The  methods  just  explained  have  gained  still  more  in 
importance  since  it  has  been  proved  that  the  indigestible 
condition  of  cow's  milk  does  not  really  arise  from  its  chem- 
ical composition,  but  from  its  "  unavoidable  contamination 
with  micro-organisms  "  which  in  some  way  or  other  cause 
disturbances  in  the  digestive  organs  of  nursing  children.* 

I  must  finally  mention  that  although  pasteurization 
will  kill  the  majority  of  bacteria,  the  danger  that  the  milk 
may  occasion  sickness  is  not  in  all  cases  entirely  removed. 
Some  bacteria  are  found  producing  poisonous  principles  by 

*  See  foot-note  on  p.  160. 


PASTEURIZATION   OF   MILK.  165 

their  living  actions,  which  are  not  destroyed  by  the  heat 
applied.* 

Fortunately  these  substances  appear  very  rarely  in  milk, 
and  seem  to  originate  from  bacteria  thriving  best  in  dark, 
filthy,  and  poorly-ventilated  places.  Sterilization  of  the 
milk  does  not,  therefore,  render  it  unnecessary  to  observe  as 
great  cleanliness  and  care  as  possible  in  the  production  and 
handling  of  the  milk. 

*  As  an  example  it  may  be  mentioned  that  a  poisonous  principle 
(tyrotoxicori)i&  sometimes  found  in  milk  (see  "  Hygisea,"  1888,  p.  695). 
In  the  case  quoted  it  had  arisen  after  the  milking,  in  milk  kept  in  a 
building  with  poor  ventilation,  the  grounds  of  which  were  exposed 
to  contamination  from  a  neighboring  slaughter-house.  The  milk 
caused  a  cholera-morbus-like  disease  in  children.  Boiling  or  sterili- 
zation did  not  diminish  the  injurious  effects  of  the  milk.  See  also 
Flugge,  "On  Sterilization  of  Milk,"  Zeitschr.f.  Hyg.,  17  (1894),  pp. 
272-342. 


PART  II. 
CREAM. 


CHAPTER  I. 
CREAM  RAISED  BY  GRAVITY  PROCESSES. 

a.  The  Old  Shallow  Setting  System.  —  In  the  old 
shallow  setting  system  of  cream  separation  the  cream  is 
allowed  to  sour  on  the  milk.  This  method  is  still  com- 
mon in  our  country  at  the  present,  the  greater  portion  of 
our  farm  butter  being  made  from  cream  raised  in  this 
way.  As  the  method  is  practised  on  most  farms  it  is  not 
attractive  ;  a  good  many  of  the  faults  to  be  found  with  it 
do  not,  however,  really  belong  to  the  method  itself,  but 
are  coincident  with  it.  The  farmer's  wife  has  generally 
to  fight  the  worst  conditions  imaginable  in  her  dairy,  es- 
pecially in  winter-time.  During  this  season  the  milk  is, 
first  of  all,  of  the  poorest  quality,  on  account  of  the  scant 
feeding.  It  is  furthermore  usually  milked  in  dark  stables, 
where  the  cows  are  standing  on  manure,  with  no  good  litter 
under  them.  It  is  natural  that  the  milk  under  these  con- 
ditions should  come  in  intimate  contact  with  dung  par- 

166 


CREAM   RAISED   BY    GRAVITY   PROCESSES.  167 

tides  and  other  filth.  The  milk-pail  also  shows  variegated 
colors,  testifying  to  slovenliness;  and  as  it  is  often  used 
for  feeding  meal  and  milk  to  the  calves,  it  is  natural 
that  it  never  dries  out  thoroughly.  The  pail  harbors 
luxuriant  bacteria  and  mold-cultures,  as  any  one  can 
satisfy  himself  if  he  places  such  a  pail  in  a  clean  room, 
where  the  air  is  fresh :  it  will  not  be  long  before  colonies- 
visible  to  the  naked  eye  may  be  seen,  especially  if  the  wood 
is  kept  moist. 

Milk  subjected  to  such  conditions  cannot  possibly 
keep  well.  If  an  effort  is  made  to  prepare  palatable,  well- 
keeping  cream  by  this  method  by  means  of  ice,  in  nine 
cases  out  of  ten  we  shall  not  succeed. 

The  conditions  in  the  dairy,  if  such  a  building  or  room 
be  kept,  are  also  such  as  to  prohibit  the  production  of 
first-class  cream.  It  is  often  dark,  dirty,  and  poorly  ven- 
tilated, and  frequently  also  used  for  other  purposes.  The 
milk  is  therefore  exposed  to  the  most  unfavorable  con- 
ditions during  the  winter  months,  and  as  a  result  good 
butter  cannot  be  produced  during  this  time. 

During  the  summer  season  matters  are  fortunately  dif- 
ferent. The  quality  of  the  milk  is  then  of  the  very  best, 
thanks  to  our  good  natural  pastures.  The  cows  are 
milked  in  the  open  air,  although  often  in  muddy  inclos- 
ures.  The  udder  and  hind-quarters  of  the  cows  are  fairly 
clean,  as  the  animals  often  have  a  chance  to  stand  in  some 
lake  or  stream,,  and  as  they  never  soil  in  the  pasture  as  in 
the  stable.  The  milk-pail  also  has  a  better  appearance, 
being  thoroughly  aired  in  light  and  sunshine.  The  con- 
dition of  the  milk-pans  is  also  very  different  in  summer- 
time. They  are  not  only  well  scrubbed,  but  are  often 
placed  outside  in  the  sunshine  with  the  churn  and  other 


168  MODERN   DAIEY   PEACTICE. 

household  utensils.  This  is  in  my  opinion  the  great 
secret  and  the  main  reason  why  farm  butter  can  be  first- 
class  and  of  good  keeping  quality  during  the  summer-time, 
in  spite  of  many  unfavorable  conditions  and  poor  facili- 
ties. As  previously  shown  sun  rays  in  a  short  time  kill 
all  bacteria.  The  putrefactive  butyric  acid  and  similar 
darkness-loving  bacteria  seem  to  be  easily  destroyed  by 
direct  sunlight.  The  lactic-acid  bacteria  are  also  sensitive 
to  their  action,  but  according  to  my  experiments  are  not 
so  easily  killed  in  sunlight  as  the  former.  The  presence  of 
lactic-acid  bacteria  in  the  milk-pans  is  not,  however,  as 
injurious  for  the  milk  as  that  of  putrefactive  and  butyric- 
acid  bacteria — a  point  which  will  soon  be  further  ex- 
plained. 

The  conditions  to  which  milk  is  subjected  during 
the  separation  of  the  cream  are  also  far  more  favorable  in 
summer-time.  The  air  in  the  dairy  is  better;  the  small 
window  usually  found  is  insignificant,  but  it  constantly 
acts  as  a  ventilator,  being  usually  left  open;  the  door  is 
also  left  open  a  large  share  of  the  day,  so  that  a  draft 
is  created.  Outside  the  door  of  the  dairy  there  is  usually 
a  lawn,  and  dust  or  dirt  from  the  surrounding  regions 
are  not  therefore  very  apt  to  be  brought  in  from  the 
outside. 

Having  now  considered  the  conditions  present  where 
the  old  shallow  setting  system  of  cream  separation  is  prac- 
tised, we  shall  consider  in  how  far  the  unfavorable  con- 
ditions for  the  keeping  quality  of  the  products  are  de- 
pendent on  the  method  itself. 

For  one  thing,  uncleanliness  does  not  at  all  belong  to 
the  method.  The  lack  of  neatness  often  found  among 
farmers  using  the  system  comes  from  their  poverty  and 


CREAM  RAISED   BY   GRAVITY   PROCESSES.  169 

lack  of  knowledge.  Give  the  farmer  more  education  and 
knowledge  and  better  conditions  of  life,  and  it  will  not  be 
long  before  the  quality  of  the  milk  and  the  whole  dairy 
business  on  the  farms  will  be  revolutionized. 

The  straining  of  milk  into  wooden  dishes  is  also  ap- 
plied in  the  Holstein  method,  which  is  still  used  in  many 
places  abroad.  It  has  been  proved  beyond  a  doubt  that 
first-class  aromatic  products  of  good  keeping  quality  may 
be  obtained  by  handling  the  milk  in  wooden  vessels. 
These  require  greater  care  in  cleaning,  and  are  therefore 
not  adapted  to  creamery  use,  but  they  have  advantages 
which  tin  vessels  lack.  As  is  well  known,  wood  is  a  poor 
conductor  of  heat,  for  which  reason  wooden  dishes  are  very 
suitable  to  the  simple  conditions  present  in  the  dairies  of 
ordinary  farms.  No  special  arrangements  are  necessary  to 
keep  the  milk  in  them  at  something  like  an  even  tempera- 
ture, and  comparatively  much  and  good  cream  is  obtained 
by  their  use. 

The  milk  is  allowed  to  sour  spontaneously  in  this 
method,  but  up  to  very  late  there  was  no  rational  and 
systematically  conducted  ripening,  even  in  the  most  modern 
dairy  methods — a  lack  which  certainly  has  not  been 
to  the  advantage  of  the  products.  The  modern  dairy 
practices  need  to  be  reformed  in  this  respect  as  well  as 
the  old-fashioned  method  here  considered.  Even  the  latter 
is  not  incompatible  with  such  a  systematic  souring,  as  we 
shall  see  later  on  in  this  book,  where  more  detailed 
directions  for  this  souring  will  be  given. 

In  this  system  of  cream  separation  the  ripening  takes 
place  at  the  same  time  as  the  cream-raising.  By  closer 
examination  this  is  found  to  possess  both  advantages  and 
disadvantages. 


170  MODERN  DAIRY  PRACTICE. 

If  we  compare  this  method  with,  e.g.,  the  Holstein 
method,  we  find  that  the  cream-raising  and  ripening  in 
the  latter  demand  a  very  long  time,  because  the  milk  is 
creamed  under  conditions  which  do  not  hasten  this  pro- 
cess and  the  cream  is  not  ripened  until  after  skimming. 
In  the  old  shallow  setting  method  these  processes  go  hand 
in  hand,  and  under  favorable  conditions  occur  more 
rapidly  than  in  the  method  just  mentioned,  especially  if 
we  consider  that  the  pans  used  by  the  farmer  hold  more 
milk  than  the  Holstein  pans — which  is  a  decided  advan- 
tage. This  method  cannot  of  course  be  compared  with 
the  centrifugal  method  as  far  as  rapidity  in  reaching 
the  result  goes;  but,  as  my  experiments  have  shown,  we 
can  obtain  a  properly  soured  cream  in  a  good  deal  shorter 
time  by  this  method  than  is  required  by  the  ice  method  if 
the  milk-room  is  kept  moderately  warm  and  a  good 
starter  is  added  to  the  milk. 

It  is  often  stated  that  a  smaller  quantity  of  butter  is 
obtained  by  the  old  shallow  setting  method  than  in  the 
modern  methods  of  cream-raising.  Repeated  direct  ex- 
periments conducted  by  me  do  not  bear  out  this  assertion, 
however.  I  shall  here  briefly  report  an  experiment  made 
last  summer. 

The  same  quantity  of  the  same  milk  was  treated  ac- 
cording to  the  separator,  the  ice,  and  the  shallow  setting 
system,  care  being  taken  in  all  cases  to  observe  the  di- 
rections for  the  different  methods  with  the  greatest  possi- 
ble accuracy.  The  milk  was  separated  at  86°  F.,  the 
separator  (de  Laval)  making  7600  revolutions  per  minute; 
the  separated  cream  was  ripened  in  the  usual  way  in 
eighteen  hours.  In  the  ice  method  the  milk  was  left  for 
twenty-eight  hours,  the  temperature  of  the  room  being 


CREAM   RAISED   BY   GRAVITY   PROCESSES. 


171 


54°  F.,  and  that  of  the  water  in  the  creamer  36°.  The 
cream  was  ripened  in  the  same  way  as  in  the  separator 
method.  In  the  shallow  setting  method  the  milk  was 
strained  into  wooden  pans  holding  about  three  quarts.  It 
was  left  for  forty-eight  hours  in  a  room  with  a  tempera- 
ture of  54°,  to  allow  the  cream  to  raise  and  the  souring  to 
take  place.  It  was  then  removed  to  another  room  with  a 
temperature  of  64°  F.,  where  it  was  kept  for  twelve  hours. 
When  the  milk  was  skimmed  the  casein  was  evenly  coagu- 
lated. The  experiment  gave  the  following  results : 


System  of  Cream-raising. 

Milk. 

Lbs. 
125.4 
125.4 

125.4 

Temper- 
ature— 

Products. 

Hours 
re- 
quired 
for 
Cream- 
rais- 
ing. 

Hours 
re- 
quired 
for 
Ripen- 
ing. 

of 
Room. 

of 
Milk. 

Cream. 

Butter. 

Separator  method 

°F. 
64 
54 

54-64 

op 

86 
36 

59 

Lbs. 
26.6 
23.8 

17.8 

Lbs. 
6.4 
5.5 

5.5 

'as' 

v  —  » 

6 

18 
18 

/ 

0 

Shallow  setting  method 

As  might  have  been  predicted,  the  yield  was  largest  in 
the  separator  method,  but  similar  quantities  of  butter 
were  obtained  in  the  two  other  methods  from  the  same 
quantity  of  milk.* 

*  Without  doubting  the  correctness  of  the  figures  given  in  the 
foregoing  experiment,  I  cannot  agree  with  the  author  that  the  old 
method  of  cream-raising  will  in  general  give  as  good  results,  as  far 
as  yield  of  butter  goes,  as  do  the  modern  methods.  The  per-cent  of 
fat  left  in  the  skim-milk  obtained  by  the  various  processes  will,  as 
it  seems,  show  that  such  cannot  be  the  case.  Skim-milk  from 
shallow  pans  set  in  the  air  in  my  experience  always  contain  over 
1  per  cent  of  fat,  often  over  1.50  per  cent;  while  deep-setting  skim- 
milk  cooled  by  water  will  contain  from  .50  to  1  per  cent  of  fat, 


172  MODERtf   DAIRY   PRACTICE. 

The  main  objection  to  this  method  is  that  the  skim- 
milk  sours  at  the  same  time  as  the  cream.  This  is  a  seri- 
ous objection  from  one  point  of  view,  but  many  farmers 
accustomed  to  the  wholesome  and  refreshing  sour  milk 
obtained  in  the  old  method  often  complain  that  they 
cannot  get  as  good,  delicious  sour  milk  when  this  is  made 
from  sweet  skim-milk.  It  is  doubtless  a  fact  that  the 
two  kinds  of  sour  milk  taste  entirely  different.  It  is  also 
natural  that  such  should  be  the  case,  for  in  one  instance 
the  milk  is  allowed  to  sour  slowly  in  a  relatively  shallow 
layer,  while  in  the  other  it  sours  rapidly  in  deep  ripening 
cans.  I  have  also  found  that  the  layer  of  cream  on  the 
milk  in  the  shallow  pans  has  a  special  influence  on  the 
acidity  and  taste  of  the  underlying  skim-milk,  evidently 
because  this  condition  favors  the  growth  and  develop- 
ment of  special  bacteria. 

A  weak  point  in  this  method  is  the  fact  that  the  skim- 
milk  can  only  be  boiled  with  difficulty.  Farmers  prefera- 
bly use  their  skim-milk  as  sour  milk,  however,  and  only 
rarely  consume  boiled  milk,  so  that  this  point  is  not  very 
important.  Another  question  on  which  I  dare  not  express 
an  opinion  is,  whether  it  would  be  right  from  a  hygienic 
point  of  view  to  agitate  against  the  abundant  consumption 
of  sour  milk  by  the  people.  In  passing  I  will  add  that 

and  cooled  by  ice  from  .20  to  .50  per  cent  of  fat.  Fleischmann 
gives  the  following  number  of  pounds  of  milk  as  required  for 
making  one  pound  of  butter :  creaming  in  high  pans  at  15°  C., 
33  Ibs.;  in  shallow  pans  at  15°  C.,  31  Ibs.;  in  the  Gussander  method 
(see  second  division  of  the  present  chapter),  29.5  Ibs.;  in  cold- 
water  setting,  the  Holstein  method,  and  Schwartz's  method,  29  Ibs. 
of  milk.  The  results  of  Fjord's  experiments  (17th  Dairy  Report, 
1882)  go  in  the  same  direction.— W. 


CEEAM   RAISED   BY   GEAVITY   PBOCESSES.  173 

a  large  number  of  infectious  bacteria  do  not  thrive  in  a 
substratum  containing  large  quantities  of  lactic  acid. 

Bacteria  in  Shallow-setting  Cream. — Proceeding  to  a 
statement  of  the  bacteria  which  my  analyses  of  cream  pre- 
pared according  to  the  shallow-setting  method  have  shown 
present,  we  first  note  that  this  cream  when  left  on  the 
skim-milk  shows  a  downy  surf  ace,  especially  when  near  the 
ripening  stage.  This  down  comes  from  a  growth  of  the 
milk-molds  (Oidium  lactis)  spoken  of  before.  The  part 
which  the  molds  play  may  be  manifold :  by  their  alkaline 
reaction  they  may  be  the  cause  of  the  lactic-acid  bac- 
teria thriving  and  living  for  a  somewhat  longer  time  in 
the  sour  cream.  These  molds  also  consume  the  acid  in 
the  upper  layer  of  the  cream,  thus  causing  a  weakening  of 
acid  in  the  lower  layers  of  the  milk,  through  which  these 
become  better  adapted  to  the  anaerobic  bacteria.  Investi- 
gations made  after  the  first  part  of  the  original  of  this 
work  was  written  show  that  if  we  want  to  study  the 
anaerobic  bacteria  of  the  milk  we  may  conveniently  seek 
them  in  just  such  milk-pans  overgrown  with  molds. 

Those  milk  fungi  furthermore  appear  to  protect  the 
milk  from  later  and  possibly  more  dangerous  infection. 
They  grow  fast  and  spread,  especially  in  tjie  upper  layers; 
and.  if  they  were  not  there,  more  dangerous  micro-organ- 
isms would  most  likely  take  their  place. 

Excepting  the  molds  mentioned,  I  have  not,  in  spite  of 
numerous  bacteriological  analyses,  been  able  to  discover 
any  micro-organisms  characteristic  of  this  cream.  The 
bacteria  found,  both  those  infecting  the  milk  as  well  as 
the  useful  and  desirable  lactic-acid  bacteria,  are  mainly 
the  same  as  those  found  in  any  other  cream  allowed  to 
sour  spontaneously.  A  couple  of  points  are,  however, 


174  MODERN   DAIRY   PRACTICE. 

to  be  observed  in  this  connection.  Bacterial  infections 
are  first  of  all,  as  a  rule,  more  numerous  in  cream  which 
has  soured  on  the  milk  than  in  that  prepared  according 
to  modern  methods.  Their  number  will  vary  greatly.  In 
examining  cream  from  the  same  milk  obtained  by  the  dif- 
ferent methods  the  shallow-setting  cream  has  usually 
been  found  richest  in  bacteria  not  producing  lactic  acid, 
although  this  was  by  no  means  always  the  case.  A  very 
small  number  of  such  bacteria  were  found  in  the  cream  if 
the  milk  had  been  strongly  infected  with  lactic- acid  bac- 
teria. The  quality  of  the  cream  was  then  as  good,  from  a 
bacteriological  point  of  view,  as  if  it  had  been  prepared 
according  to  the  ice  method,  and  often  better.  The  ex- 
planation is  doubtless  to  be  found  in  the  fact  that  the 
early-appearing  mass-infection  (see  p.  93)  of  lactic-acid 
bacteria  hindered  the  growth  of  other  bacteria.  In  this 
way  the  ripening  took  place  rapidly  and  at  the  same  time 
as  the  raising  of  the  cream,  so  that  if  the  infection  took 
place  at  the  proper  time  the  cream  was  sufficiently  sour 
and  coagulated  just  at  the  end  of  the  separation. 

Another  point  to  be  noticed  is  that  yeast-fungi  taking 
part  in  the  starting  of  the  lactic-acid  fermentation  have 
been  found  only  in  the  cream  and  sour  milk  from  small 
farm-dairies.  I  have  found  such  yeasts  in  "  stringy  "  milk 
from  Borgaa  and  in  buttermilk  from  Savolaks  and 
Karelen. 

Very  different  kinds  of  lactic-acid  bacteria  may  appear 
at  the  same  time  in  the  sour  milk  and  cream  on  neighbor- 
ing farms.  A  fact  which  will  be  further  considered  when 
the  question  of  cream-ripening  comes  up  is  that  in  some 
farm-dairies  I  have  met  with  buttermilk  containing  prac- 
tically only  lactic-acid  bacteria.  These  samples  of  butter- 


CREAM   RAISED   BY   GRAVITY   PROCESSES.  175 

milk  originated  on  particularly  well-conducted  farms, 
where  the  housewife  herself  took  care  of  the  milk.  By 
accident  I  learned  of  one  of  these  farms  that  it  had  the 
reputation  of  making  first-class,  well-keeping  butter.  A 
separation  and  ripening  of  the  cream  according  to  this 
method  can  therefore  be  well  conducted  and  give  good 
results. 

Having  studied  the  conditions  of  this  method  of  cream- 
raising,  and  learned  how  bacteria  generally  appear  in  the 
cream,  we  shall  briefly  consider  its  keeping  quality.  From 
the  point  alone  just  mentioned,  that  such  cream  is  gener- 
ally mixed  with  a  great  number  of  non-lactic-acid-produc- 
ing bacteria,  we  may  conclude  that  usually  it  will  not 
keep  long;  but  we  have  seen  that  under  favorable  condi- 
tions cream  may  also  be  obtained  by  this  method  which 
will  contain  practically  pure  cultures  of  lactic-acid  bac- 
teria. How  this  exceptional  condition  may  become  the 
rule,  or  at  least  more  general,  will  be  shown  in  a  later 
chapter.  From  the  description  given  it  will  be  seen  that 
it  has  its  good  points,  and  that  the  method  hardly  deserves 
the  scorn  shown  it  by  writers  and  speakers  on  dairy  topics. 

b.  The  Modern  Systems  of  Gravity  Creaming. — In  the 
more  modern  creaming  methods  neither  cream  nor  skim- 
milk  undergoes  any  appreciable  change  during  the  cream- 
ing. The  principle  both  in  these  methods  (the  Holstein, 
Gussander,  Swartz,  and  Cooley  methods),  as  well  as  in  the 
separator  and  extractor  methods,  to  be  considered  in  the 
next  chapter,  is,  that  the  fermentation  bacteria  are  not  al- 
lowed to  develop  to  any  appreciable  extent,  either  before 
or  during  the  rising  and  separation  of  the  cream. 

Two  objects  have  constantly  been  kept  in  view  in  the 
older  of  these  methods:  to  favor  the  rising  of  the  cream, 


176  MODERN   DAIRY    PRACTICE. 

and  as  far  as  possible  to  prevent  the  fermentation  bacteria 
from  developing  their  specific  functions.  We  shall  here 
dwell  mainly  on  the  latter  object. 

As  we  have  seen,  the  milk  always  contains  a  larger  or 
smaller  number  of  bacteria  when  set.  According  to  my 
experiments  the  number  of  bacteria  in  cream  from 
Swartz's  cans  may  vary  from  less  than  1 00  to  several  tens 
of  thousands  per  cubic  centimeter — the  conditions  of 
creaming  being  the  same  in  all  cases.  The  variation  de- 
pended entirely  on  the  handling  of  the  milk  before  setting. 
If  the  milk  has  been  handled  with  the  greatest  cleanliness 
and  according  to  the  principles  previously  dwelt  on,  the 
number  of  bacteria  in  the  cream  will  not  only  be  smaller, 
but  the  bacteria  found  will  not  as  a  rule  be  of  such  unde- 
sirable forms  as  will  otherwise  be  the  case. 

The  means  at  hand  for  the  checking  of  the  fermenta- 
tion bacteria  during  cream-raising  are,  of  course,  the  same 
as  stand  at  our  disposal  in  the  keeping  of  the  milk,  viz. : 

1.  Scrupulous  cleanliness  throughout  the  dairy,  es- 
pecially as  regards  the  creaming-vessels,  etc.  2.  Cooling 
the  milk  as  quickly  as  possible;  and,  3.  Light,  fresh,  and 
dry  creaming-rooms. 

The  lactic-acid  organisms  are  generally  best  fought  by 
the  first  two  methods,  but  the  last  method  also  tends  to 
check  them,  though  not  to  the  extent  in  which  it  checks 
putrefactive  and  similar  bacteria. 

The  oldest  method  of  creaming  of  this  kind  is  the 
Holstein  system.  In  this  method  the  complete  rising  of 
the  cream  is  secured  by  the  thinness  of  the  layer  of  milk 
and  by  a  rather  high  temperature,  at  which  the  milk-serum 
is  but  little  viscous.  The  development  of  the  bacteria 
is  rather  incompletely  checked.  The  temperature  sinks 


CREAM   RAISED   BY   GRAVITY   PROCESSES.  177 

slowly  in  the  pans,  and  the  final  temperature  (55°-59°  F.), 
while  not  very  favorable  to  the  bacteria,  is  yet  by  no  means 
unfavorable;  and  as  the  milk  is  under  the  influence  of  this 
and  still  higher  temperature  for  at  least  thirty-six  hours, 
it  is  evident  that  a  considerable  bacterial  growth  will  take 
place.  It  is  also  often  very  difficult  in  this  method  to 
fight  especially  the  lactic-acid  bacteria,  and  older  writers 
on  dairy  matters,  as  Martens,  dwell  at  length  on  the  diffi- 
culty of  keeping  the  milk  and  the  cream  sweet  when  this 
method  is  followed.  The  difficulty  of  keeping  the  wooden 
pans  clean  is  another  objection  to  the  method.  Martens 
also  maintains  as  the  first  duty  of  the  dairywoman  "  to 
have  especial  attention  directed  toward  the  cleaning  of 
the  dairy  utensils.  She  should  always  be  present  at  the 
cleaning  of  the  milk-pans  and  personally  examine  every 
pan." 

In  spite  of  these  disadvantages,  the  method  when 
properly  conducted  gives  excellent,  well-keeping  butter. 
The  explanation  doubtless  is  found  in  the  minute  cleanli- 
ness and  dryness  (see  p.  112)  which  must  be  observed  where 
it  is  used. 

In  the  Gussander  method,  invented  in  the  '40's  by 
Major  Gussander  in  Sweden,  the  milk  is  strained  in  still 
thinner  layers  than  in  the  preceding  method,  and  the  tem- 
perature is  generally  higher.  The  rising  of  the  cream  is 
facilitated  by  the  short  distance  to  the  surface  and  by  the 
lower  viscosity  of  the  medium  through  which  it  has  to  pass. 
The  milk  is  here  not  kept  in  cellars,  as  in  the  Holstein 
method,  where  a  certain  moisture  of  the  atmosphere  is 
likely  to  be  retained,  but  in  light,  cheerful  rooms,  where 
scrupulous  cleanliness  is  observed,  and  where  fresh,  dry  air 
can  all  the  time  be  maintained.  Cleanliness  was  also  fa- 


178  MODERN"   DAIRY   PRACTICE. 

cilitated  by  introducing  metal  vessels  in  the  creaming  of 
the  milk. 

The  weak  point  in  this  otherwise  attractive  method  is 
evidently  the  high  temperature  in  the  milk-room,  for  which 
reason  the  milk  also,  according  to  numerous  testimonies, 
was  very  apt  to  sour.  It  is  natural  that  the  lactic-acid 
bacteria  under  such  conditions  would  get  the  upper  hand 
of  other  milk  bacteria.  Putrefactive  and  similar  bacteria 
had  very  poor  chances  of  life  in  a  Gussander  milk-room. 

In  the  ice  method,  now  generally  used  in  our  dairies, 
light  and  cleanliness  are  the  main  weapons  for  fighting 
the  fermentation.  But  the  bacteria  are  further  checked  in 
this  method  by  cooling  the  milk.  As  before  stated,  the 
low  temperature  checks  the  growth  and  development  of 
the  bacteria,  but  it  does  not  kill  them.  If  the  cooling  is 
neglected  or  conducted  so  slowly  that  the  bacteria  present 
in  the  milk  or  in  unclean  vessels  are  allowed  to  develop 
and  multiply  before  the  temperature  is  low  enough  to  stop 
these  processes,  injurious  changes  in  the  milk  or  its  prod- 
ucts may  sooner  or  later  be  observed.  If  the  cream  does 
not  become  appreciably  sour  or  of  an  undesirable  flavor  by 
such  manner  of  procedure,  it  will  still  be  found  that  the 
butter  made  from  the  cream  is  not  of  the  good  quality  it 
would  otherwise  have  been. 

From  the  results  obtained  in  the  laboratory  at  Eiitti 
(p.  88)  we  find  how  immensely  quicker  and  stronger  the 
development  of  bacteria  will  take  place  in  milk  of  77°  F. 
than  in  milk  18°  lower.  If  still  lower  temperatures  had 
been  applied  it  would  have  been  found,  as  in  my  experi- 
ments (p.  89),  that  the  development  decreased  more  rapidly 
the  further  the  milk  was  cooled  down,  and  that  it  stopped 
entirely  at  39°  F.  (4°  0.). 


CREAM   RAISED   BY   GEAYITY   PROCESSES.  179 

In  the  ic<  method  the  milk  is  creamed  in  high,  usually 
narrow  tin  cans.  These  cans  are  easily  cleaned  and 
steamed,  and  it  is  therefore  not  difficult  to  keep  them 
sterile. 

Without  entering  into  a  general  discussion  of  the  ad- 
vantages of  this  method  in  our  creameries  and  dairies,  I 
desire  to  call  attention  to  some  points  about  it,  the  neg- 
lect of  which  will  largely  influence  the  keeping  quality  of 
the  products. 

First  of  all,  I  will  recall  what  was  said  on  pp.  62-66 
concerning  the  necessity  of  the  rapid  cooling  of  the  milk 
by  the  use  of  sufficient  quantities  of  ice.  It  is  necessary 
not  only  to  use  ice  liberally,  but  to  use  it  in  the  right  way. 
It  is  therefore  advisable  to  have  finely-divided  ice  in  the 
creamer  instead  of  large  pieces,  especially  in  the  first  cool- 
ing of  the  milk,  as  the  fine  ice  causes  a  more  rapid  cool- 
ing of  water  and  milk.  When  a  sufficient  decrease  in  the 
temperature  of  the  milk  has  been  obtained,  larger  pieces 
of  ice  may  be  used.  A  mistake  often  made  is  to  place  the 
milk-cans  very  near  one  another,  not  allowing  a  sufficient 
quantity  of  ice  between  them  for  the  rapid  cooling  of  the 
milk.  It  may  furthermore  be  well  to  remember  that  pure 
water  must  be  kept  in  the  creamer.  In  many  creameries 
the  same  water  is  left  in  the  tanks  for  weeks,  although 
milk  is  often  spilled  into  them,  thus  improving  the  water  as 
a  nutritive  medium  for  bacteria.  The  water  is,  of  course, 
kept  cold  by  the  ice  floating  in  it,  and  the  bacteria  are 
thus  prevented  from  increasing  perceptibly;  but  water 
often  splashes  into  the  milk  from  the  creamer  or  is  spilled 
on  the  floor  and  walls,  where  it  evaporates.  The  bacteria 
coming  from  the  evaporated  water  may  then  float  in  the 
air,  and  thus  easily  infect  the  milk, 


180  MODERN    DAmY    PRACTICE. 

\ 

Cream  obtained  by  the  ice  method  contains  compara- 
tively few  bacteria,  except  in  cases  where  the  milk  before 
setting  was  highly  infected,  or  where  sufficient  cooling  was 
not  practised.  We  seldom  find  molds  in  it  and  never 
o'idium  fungi,  as  in  case  of  cream  obtained  by  the  shallow- 
setting  system.  At  the  temperature  used  in  the  ice 
method  the  molds  can  evidently  not  develop  in  the  cream 
layer  and  form  long,  threadlike  conidia,  giving  the  cream 
a  "  velvety  "  appearance. 

rfhis  system  of  cream-raising  has  an  immense  advan- 
tage over  those  previously  described  as  regards  the  ease  of 
combating  the  fermentation  germs  by  the  cooling  process. 
If  this  is  properly  conducted,  bacterial  growth  may  be 
pr^cffecally  stopped,  and  no  fermentations  will  set  up. 
There  is  always  a  danger  in  this  respect,  however,  as  is 
plain  from  the  fact  that  some  milk  bacteria  will  reproduce 
at  a  temperature  of  50°  F.  (10°  C.).  Care  must  therefore 
be  exercised  in  using  the  method  if  first-class  results  are 
wanted.  But  if  the  directions  given  are  carefully  followed 
andXSe  milk  on  hand  has  not  already  been  overloaded 
with  bacteria,  we  may  feel  assured  that  the  keeping 
quality  of  the  products  will  not  be  diminished  during  the 
cream  separation— a  result  which  cannot  be  reached  in  any 
of  the  other  methods  so  far,  described, 
i  • 

r 

/ 

s. 


CHAPTER  II. 
SEPARATOR  CREAM. 

THE  centrifugal  method  rests  on  an  entirely  different 
principle  from  those  previously  considered.  The  heavier 
parts  of  the  milk,  the  skim-milk,  are  whirled  against 
the  circumference  of  a  rapidly-rotating  steel  bowl,  while 
its  lighter  parts,  the  cream,  remain  nearer  the  centre. 
The  result  is  that  not  only  is  the  cream  separated  from 
the  skim-milk,  but  all  filthiness  present  in  the  milk  is 
also  forced  to  the  wall,  where  it  forms  a  tough,  sticky 
layer,  called  "separator  slime."  The  separation  takes 
place  in  the  manner  mentioned,  both  in  the  cream  sepa- 
rator and  the  extractor. 

By  application  of  the  separator  method  the  cream  may 
be  separated  from  the  milk  as  soon  as  this  comes  to  the 
creamery.  The  time  of  infection  is  greatly  shortened,  the 
chances  of  contamination  of  bacteria  decreased,  and  the 
bacteria  already  found  in  the  milk  do  not  get  time  to 
develop.  For  these  reasons  this  method  possesses  a  de- 
cided advantage  over  all  other  methods  of  cream  separa- 
tion known. 

At  a  large  number  of  separator  creameries  in  this  and 
other  countries  this  point  is  not  taken  advantage  of,  how- 
ever, as  we  often  find  that  the  milk,  which  is  usually 
warm  when  it  comes  to  the  creamery,  is  left  for  hours  in 
the  hauling-cans,  whereby  of  course  its  bacteria  have  an 

181 


182  MODERN    DAIRY   PRACTICE. 

excellent  chance  to  increase  and  start  their  characteristic 
fermentations.  In  many  places  this  is  done  from  igno- 
rance; in  other  places  because  the  number  or  capacity  of 
the  separators  do  not  correspond  to  the  quantity  of  milk 
received.  If  the  danger  involved  in  such  treatment  of  the 
milk  was  properly  understood,  the  expense  of  buying  a 
sufficient  number  of  separators,  or  separators  of  sufficient 
capacity,  would  not  be  considered. 

We  saw  on  page  68  the  advantage  of  pasteurizing  the 
unskimmed  milk  to  be  hauled  away,  so  as  to  increase  its 
keeping  quality.  Pasteurization  of  milk  is  also  often  prac- 
tised for  another  purpose — viz.,  to  obtain  butter  that  will 
keep  better.  It  is  both  expensive  and  a  waste  of  time  to 
separate  the  cream  from  such  pasteurized  milk  by  means  of 
any  of  the  older  methods,  while  it  may  easily  be  done  by 
application  of  the  centrifugal  method.  Pasteurization  of 
the  milk  before  separation  not  only  gives  a  product  that 
will  keep  better,  but  also  brings  about  another  advantage, 
as  shown  by  Borje  Norling:  the  production  of  a  thinner 
skimmed  milk — i.e.,  the  cream  is  richer  in  fat.  This 
writer  advises  that  new  milk  be  first  pasteurized,  then 
separated  at  about  159°  F.,  the  cream  and  the  skimmed 
milk  to  be  cooled  in  separate  coolers.  He  states  that 
numerous  comparative  trials  have  shown  that  if  milk 
is  skimmed  under  similar  conditions  partly  at  common, 
partly  at  pasteurization  temperature,  the  skim-milk  will 
regularly  show  a  lower  fat  content  in  the  latter  case.* 
The  method  of  pasteurizing  the  new  milk  before  the 

*  Limde  found  in  his  pasteurization  experiments  the  following 
average  percentages  of  fat  in  the  skim-milk,  the  speed  and  amount 
of  milk  run  through  the  separator  being  the  same  in  both  cases  : 
skim-milk  from  pasteurized  milk,  .14  per  cent;  from  non-pasteurized 


SEPARATOR  CREAM.  183 

separation  has  proved  less  advantageous  in  my  experi- 
ments, because  the  cream  to  a  great  extent  transmitted 
the  cooked  taste  to  the  butter.  This  was  not  the  case 
when  only  the  cream  was  pasteurized,  although  the  temper- 
ature was  the  same  in  both  cases.  The  difference  doubtless 
came  from  the  fact  that  a  quicker  cooling  could  be  applied 
in  the  latter  case.  As  I  consider  the  presence  of  a  cooked 
taste  in  butter  a  very  serious  fault,  I  cannot  recommend 
pasteurizing  milk  intended  for  butter  production,  and  shall 
not  therefore  here  enter  into  the  details  of  the  process. 

Distribution  of  Bacteria  in  the  Centrifugal  Process. 

The  centrifugal  method  has  still  another  advantage 
over  the  old  methods  of  cream  separation, — an  advantage 
of  which  is  thought  too  little,  viz.,  the  ability  to  remove  a 
large  number  of  bacteria  in  the  milk,  so  that  the  separated 
cream  and  skim-milk  do  not  (as  in  the  most  favorable  in- 
stances in  the  older  methods)  contain  the  number  of  bac- 
teria which  were  found  before  the  cream  was  separated 
from  the  milk,  but  contain  even  a  smaller  number  than 
before  separation.  I  have  verified  in  numerous  trials  that 
a  large  number  of  the  bacteria  present  in  the  milk  treated 
were  removed  from  the  cream  and  the  skim-milk  by  the 
centrifugal  force  and  went  into  the  separator  slime.  This 
can  be  ascertained  by  comparing  the  number  of  bacteria 
found  in  the  milk  before  the  separation  with  the  number 
found  in  the  cream,  skimmed  milk,  and  separator  slime 
after  the  separation.  I  have  made  numerous  examinations 
of  this  kind,  experimenting  with  milk  poor  in  bacteria 

milk,  .22  per  cent  fat — the  former  analyses  ranging  from  .11  to  .17 
per  cent  and  the  latter  from  .18  to  .35  per  cent.— W. 


184 


MODERN   DAIRY   PRACTICE. 


as  well  as  with  samples  containing  an  immense  number 
of  them.  The  following  table  shows  the  results  of  some  of 
these  investigations: 


Origin  of  Milk. 

Number  of  Bacteria  per  Cubic  Centimeter. 

In  New 
Milk. 

In  Skim- 
milk. 

In  Cream. 

In  Separator 
Slime. 

Mixed  evening  and  morning 
milk  ;  

18,180 
6,500 
4,100 
1,890 
1,530 
1,640 
1,030 

11,025 
2,025 
2,300 
680 
650 
360 
220 

13,200 
3,800 
2,480 
550 
480 
450 
200 

4,241,000 
1,320,000 
836,000 
560,600 
650,000 
150,800 
230,000 

it 

tt 

tt 

ft 

ti 

It  is  very  peculiar  that  the  cream  in  most  of  the  above 
experiments  contained  a  larger  number  of  bacteria  than 
the  skim-milk.  I  cannot  explain  this  phenomenon.  It  is 
apparent,  however,  that  even  the  cream  has  been  appreci- 
ably freed  from  bacteria  and  thus  improved  in  keeping 
quality.  The  immense  number  of  micro-organisms  in  the 
slime  gives  also  evident  proof  thereof.* 

*  Weiginann  (Ldw.  Jahrb.,  Erg-Band  I,  ,.  57;  Molkerei-Zeituug 
8  (1894),  p.  371)  and  Scheurlen  (Arb.  Kaw.  Oes.  Amtes  7  (1891),  p. 
269;  Fuhling's  Idw.  Zeilung,  1892,  p.  575  ;  Zettschr.  f.  Nalirungsm. 
Unters.,  1893,  p.  3)  found  that  by  far  the  greater  portion  of  the 
bacteria  goes  into  the  cream  by  the  centrifuging,  and  only  a  minute 
quantity  goes  into  the  slime.  Wyss  (Tagb.  d.  62.  Versam.  Deut. 
Naturf.,  1890;  CentralbL  f.  Bact.,  VI.  p.  587)  found  seven  times  as 
many  bacteria  in  the  slime  as  in  the  centrifuged  milk,  and  Gernhardt 
(Inaug.  Dissert.  Univ.  Jurjew,  1893,  p.  76)  found  three  to  four  times 
as  many.  It  is  possible  that  the  point  mentioned  by  the  author  in 
the  following  paragraph  (see  above)— the  varying  bacteria  content 
of  the  milk— accounts  for  the  difference  in  the  results  obtained  by 
the  different  investigators.— W. 


SEPARATOR  CREAM.  185 

Another  observation  made  in  this  investigation  which 
is  also  shown  in  the  above  table  is  that  the  fewer  bacteria 
the  milk  contains  the  more  completely  has  the  separation 
purified  the  cream  and  the  skim-milk.  We  are  here  again 
cautioned  to  observe  greater  care  and  cleanliness  throughout 
the  handling  of  the  milk.  The  cleaner  the  milk  we  start 
with,  the  greater  are  the  advantages  offered  by  the  facili- 
ties in  the  dairy  for  keeping  the  milk  good,  and  the 
better  keeping  products  we  obtain;  while,  on  the  other 
hand,  as  has  often  been  stated,  slovenliness  in  the  handling 
of  the  milk  during  the  early  stages  stamps  its  mark  even 
on  the  subsequent  manufacturing  processes  and  renders 
them  much  more  difficult. 

The  greater  portion  of  the  separator  slime  is  made  up 
of  the  microscopic  filthiness  deposited  on  the  inside  of  the 
separator  bowl  as  a  sticky  mass,*  the  quantity  of  which 
varies  according  to  the  treatment  of  the  milk.  In  my  in- 
vestigations this  sticky  layer  has  amounted  to  not  less 
than  .1  to  .3  per  cent  of  the  weight  of  the  new  milk.f 
This  large  quantity  of  filth  will  remain  in  the  cream  and 
the  skim-milk  in  using  any  of  the  methods  of  cream  sepa- 
ration mentioned  above — a  point  too  little  considered,  in 
which  the  centrif uga  ^method  has  a  decided  advantage  over 
its  predecessors.  This  point  alone  is  in  my  opinion  so  im- 
portant and  valuable  that  it  might  speak  for  the  universal 
adoption  of  the  separator  method. 

It  must  be  observed,  however,  that  the  separators  can- 

*  See  further  "  Afbildningar  af  komjolk,"  etc.,  p.  12. 

f  Fleischmanii  (Jahresb.  Agr.  Chemie,  1885,  p.  619)  obtained 
from  .04  to  .13  per  cent  of  slime,  and  Scheuerlen  (Zeitschr.  f. 
Nahrungsm.  Unters.,  1893,  p.  3)  about  .04  per  cent  (130  grams  from 
300  liters  of  milk).—  W. 


186  MODERN    DAIRY   PRACTICE. 

not  retain  a  too  thick  layer  of  slime  in  the  bowl,  and  if 
much  filth  is  accumulated  on  it,  part  of  it  will  again  be 
washed  off  and  will  mix  in  the  cream  and  the  skim-milk. 
To  prevent  this  new  infection  we  must  avoid  running  the 
separators  many  hours  without  interruption,  and  special 
attention  must  be  given  to  their  cleaning.  When  con- 
ducted in  the  right  way  the  separation  will,  however,  im- 
prove the  milk,  decrease  its  bacterial  content,  clean  it  and 
make  it  keep  better. 

The  results  of  my  investigations  thus  differ  from  those 
obtained  by  Professor  Fjord  in  Denmark  in  his  investiga- 
tions of  separator  skim-milk,  where  he  found  that  centri- 
fuging  the  milk  neither  injures  nor  improves  its  keeping 
quality.  He  doubtless  worked  with  highly-infected  milk 
containing  large  quantities  of  bacteria  even  after  the 
separation,  and  these  soon  made  their  influence  felt  at  the 
high  temperature  applied. 

The  nature  of  the  different  bacteria  may  also  be  of  some 
importance  in  regard  to  this  question.  In  making  similar 
boiling  experiments  of  separator  skim-milk  as  conducted  by 
Fjord  in  the  investigation  mentioned,  I  have  as  a  rule  been 
able  to  prove  a  very  high  keeping-quality  in  the  separator 
milk.  Exceptions  always  occurred  in  cases  where  the  milk 
was  very  rich  in  bacteria  before  the  separation. 

[Scheuerlen  has  also  shown  that  even  strong  separation 
only  partially  purifies  a  highly  infected  milk  from  bacteria, 
and  different  kinds  of  bacteria  behave  differently  under  the 
influence  of  centrifugal  force.  He  calls  special  attention  to 
the  fact  that  tubercle  bacilli  and  some  lactic-acid  bacteria 
are  easily  separated  into  the  slime  in  separation,  while,  e.g., 
the  typhus  bacillum  is  usually  found  in  the  cream.*] 
*  Author's  addition  to  American  translation. 


SEPARATOR  CREAM.  187 

In  his  investigations  of  tuberculous  milk  Bang  did  not 
succeed  in  purifying  it  entirely  from  bacilli  by  means 
of  the  centrifuge.  I  also  have  been  unable  to  remove  all 
bacteria  from  milk  infected  with  the  ordinary  milk  bac- 
teria by  means  of  separation.  If  we  cannot  obtain  milk 
free  from  bacteria  by  the  use  of  centrifugal  force  as  ap- 
plied in  our  ordinary  separators,  it  does  not  follow  that 
the  decrease  in  the  bacterial  content  of  the  milk  before 
spoken  of  is  of  little  importance.  In  case  of  infectious 
bacteria,  as  in  Bang's  investigations,  the  results  proved 
on  the  whole  of  small  account,  as  milk  but  slightly 
tuberculous  must  be  considered  injurious  to  health.  But 
the  matter  is  quite  different  in  case  of  fermentation  bac- 
teria: the  fact  alone  that  their  number  is  decreased  by 
the  separation  makes  this  method  decidedly  better  than 
all  other  methods  of  cream-separation  now  known. 

The  cream  having  been  freed  from  a  large  number  of 
its  bacteria  in  the  separator  process,  we  must  see  to  it  that 
the  advantage  gained  is  not  lost  through  bad  treatment. 
The  danger  is  here  great  from  the  beginning,  as  the  tem- 
perature of  the  newly-separated  cream  is  very  favorable  to 
the  development  of  the  bacteria,  the  temperature  of  the 
milk  when  separated  being  usually  about  86°  F.  (30°  0.). 
We  cannot  therefore  be  surprised  that  the  cream  will  soon 
be  filled  with  a  large  number  of  bacteria  if  its  temperature 
is  not  rapidly  lowered. 

As  both  the  cream  and  the  skim-milk  come  from  the 
separator  in  thin  streams  they  offer  a  large  surface  of  in- 
fection, and  it  is  therefore  absolutely  necessary  not  to 
allow  dirty  or  dusty  persons  to  approach  the  separator; 
this  is,  however,  permitted  to  pass  unnoticed  in  many  of 
our  creameries.  The  air  in  the  separator-room  must  for 


188  MODERN   DAIRY   PRACTICE. 

the  same  reason  be  kept  pure  and  fresh;  the  cream-can 
must,  of  course,  be  as  clean  as  possible,  and  preferably 
recently  sterilized  by  steaming. 

But  these  precautions  alone  will  not  suffice.  We  must 
also  take  measures  to  act  directly  on  the  bacteria  found  in 
the  newly-separated  cream,  and  check  their  growth.  The 
measures  applicable  for  this  purpose  are  well  known  from 
the  preceding.  One  is  the  rapid  cooling  of  the  cream  to 
a  temperature  at  which  bacteria  do  not  develop,  and  the 
other  is  pasteurization  and  subsequent  rapid  cooling  of  the 
cream . 

Both  these  methods  of  preserving  the  cream  are  at  the 
present  too  seldom  applied  in  our  creameries;  there  is  no 
doubt  that  great  harm  is  done  by  the  neglect  of  these 
precautions,  for  we  may  easily,  at  this  point  in  handling 
the  milk  products,  lose  all  that  has  been  gained  by  pre- 
vious care  and  neatness  in  stable  and  dairy,  and  by  the 
separation. 

Cooling  the  Cream. — The  advantage  in  cooling  the 
cream  need  not  here  be  further  dwelt  upon :  cream  acts 
in  this  way  just  as  milk  does,  so  that  what  was  said  con- 
cerning its  cooling  is  true  also  in  case  of  cream. 

When  the  separator  method  was  introduced  in  the 
creameries  it  was  believed  that  cooling  would  not  be  neces- 
sary immediately  after  the  separation,  and  it  was  expected 
that  less  ice  would  be  needed  in  the  creamery  as  a  result. 
Experience  soon  proved  this  to  be  erroneous,  however. 
The  products  would  not  keep  well,  and  were  not  first-class. 
Then  the  cream  and  skim-milk  were  cooled,  and  the 
quality  of  the  products  was  immediately  improved.  It  is 
now  considered  a  maxim  that  the  cream  must  be  cooled  as 
soon  as  it  comes  from  the  separator. 


SEPARATOR   CREAM.  189 

We  must  not  imitate  foreign  creamery-men  in  this 
respect,  for  they  greatly  neglect  the  proper  cooling  of  the 
cream;  the  reason  of  this  is  not  that  they  are  blind  to  the 
importance  of  the  cooling  process,  but  they  have  only  limited 
means  of  cooling.  It  is  not  sufficient  to  lower  the  tem- 
perature of  the  cream  to  50°-54°  R,  as  is  done  in  many 
places.  The  consistency  of  the  butter  is  fairly  good 
even  with  such  a  cooling  of  the  cream,  but  the  keeping 
quality  is  often  not  what  it  ought  to  be.  A  full  step  must 
be  taken,  and  the  temperature  lowered  below  50°  F.,  or 
still  better  below  43°  F.  A  good  result  may  then  more 
confidently  be  expected.  But  the  consumption  of  ice  with 
this  application  of  the  separator  method  is  of  course  con- 
siderable. 

In  this  connection  I  want  to  call  attention  to  a  bad 
practice  which  is  followed  at  some  creameries  where  the 
cream  is  heated  to  167°-176°  F.  In  order  that  the  con- 
sumption of  ice  be  not  excessive,  the  warm  cream- can  is 
left  to  cool  slowly  in  a  cooling  tank  filled  with  cold  water. 
This  cooling,  however,  takes  place  too  slowly.  If  good 
coolers  are  not  at  hand,  it  is  absolutely  necessary  to  cool 
the  cream  in  tanks  filled  with  iced  water,  the  cream  being 
stirred  all  the  time  so  that  the  cooling  may  take  place 
through  the  entire  quantity.  The  method  of  cooling 
the  cream  in  the  open  air  is  not  to  be  recommended,  as  in 
this  manner  it  may  easily  be  infected  by  dust  and  bac- 
teria. 

Many  different  kinds  of  apparatus  for  cooling  the  cream 
are  found.  The  Lawrence  cooler  (see  p.  64,  Fig.  20)  is 
not  very  practical  for  this  purpose,  the  cooling  progress- 
ing too  slowly.  The  coolers  working  in  connection  with 
the  pasteurizing  apparatus  to  be  mentioned  in  next  chapter 


190  MODERN   DAIRY   PRACTICE. 

seem  preferable.  Fig.  26  shows  a  Danish  cooler  which 
offers  a  large  surface  for  the  cooling.  In 
using  this  apparatus  the  cream  is  poured 
into  the  reservoir  A,  the.bottom  of  which 
is  provided  with  several  holes  through 
which  the  cream  is  conducted  in  a  thin 
layer  over  the  cooling  cylinder  B.  The 
cooled  cream  is  gathered  in  the  basin  (7, 
and  removed  from  it  through  the  faucet 
D.  The  water  used  for  cooling  is  con- 
ducted into  the  cylinder  at  E,  and  circu- 
FlG-  26-  lates  through  the  spirals. 
Pasteurization  of  Cream. — Considering  the  second  of 
the  measures  mentioned  for  checking  bacterial  develop- 
ment in  the  newly-separated  cream,  viz.,  pasteurization, 
we  note  first  of  all  that  this  operation  must  be  conducted 
so  that  the  butter  made  from  the  cream  does  not  assume  a 
cooked  taste.  For  this  reason  the  pasteurization  must  be 
made  with  special  precautions.  To  avoid  the  cooked  taste 
in  butter  it  is  often  directed  not  to  heat  the  milk  above 
150°-158°  F.,  but  in  this  way  the  power  of  pasteurization 
to  destroy  bacteria  is  in  no  small  degree  diminished. 
According  to  my  experiments  we  may  safely  heat  the  cream 
to  165°-176°  F.  (75°-80°  C.),  provided  either  rapid  and 
strong  cooling  is  practised  immediately  after  the  pasteuri- 
zation, or  the  cream  ripened  in  a  proper  manner.  I  shall 
later  on  describe  the  latter  method. 

As  regards  the  rapid  cooling  of  cream,  my  experiments 
have  shown  that  the  cooked  taste  does  not  seem  to  reap- 
pear in  the  butter  if  the  cream  is  cooled  to  39°  F.  im- 
mediately after  pasteurization.  It  may  again  be  warmed 
to  the  temperature  of  ripening  immediately  after  the 


SEPARATOR  CREAM.  191 

pasteurization;  an  intense  cooling  seems  to  be  the  main 
point. 

The  cooling  is  beneficial  in  another  respect  as  well,  viz., 
in  preventing  the  bacteria  of  the  cream  from  developing. 
Here  we  again  meet  the  same  conditions  as  recently  at  the 
separation.  The  pasteurization  does  not  kill  all  bacteria 
in  the  cream,  nor  is  the  separation  able  to  remove  all 
bacteria  from  the  same;  it  is  therefore  in  both  cases 
equally  important  to  prevent  the  bacteria  remaining  after 
the  operations  from  developing.  I  must  also  emphasize 
that  heating,  as  far  as  the  keeping  quality  of  the  cream  goes, 
has  proved  of  but  little  benefit  if  not  followed  by  rapid 
and  efficient  cooling.  The  pasteurization  may  be  easily 
conducted  without  expensive  apparatus  in  small  or  me- 
dium-sized creameries,  if  only  the  person  to  whom  the 
operation  is  entrusted  is  sufficiently  painstaking.  There 
are  always  smaller  quantities  of  cream  than  of  skim-milk  in 
creameries,  and  the  latter  therefore  calls  for  apparatus  of 
larger  capacity.  In  case  of  pasteurization  of  cream,  on 
the  other  hand,  we  may  adopt  simpler  methods,  e.g.,  to 
place  the  cream  can  into  boiling  water,  and  thus  heat  the 
cream  to  the  desired  temperature.  Steam  must  not  be 
conducted  directly  into  the  cream,  as  this  will  dilute  it. 
In  the  method  given  the  cream  ought  to  be  stirred  fre- 
quently, as  the  desired  temperature  will  then  be  sooner 
reached.  This  is  important,  for  if  the  heating  is  done 
slowly  the  cream  will  assume  an  intense  cooked  or  "  beany  " 
taste,  which  will  reappear  in  the  butter.  A  method  which 
will  secure  more  rapid  heating  is  to  place  the  cream-can 
in  a  wooden  reservoir  whose  cover  is  provided  with  a  hole 
into  which  the  can  fits  rather  snugly.  Steam  is  intro- 
duced in  the  space  between  the  wood  and  the  can  from  a 


192  MODERN   DAIRY   PRACTICE. 

pipe,  and  the  cream  is  stirred  with  a  cream  spade  during 
the  operation.  This  method  of  heating  the  cream  has 
been  employed  for  more  than  ten  years  at  several  Finnish 
creameries  where  "  Paris  butter  "  is  made. 

Special  pasteurization  apparatus  for  cream  are  also 
found  in  the  trade,  and  the  better  ones  seem  to  serve  the 
purpose  very  well.  As  the  apparatus  used  for  pasteuriza- 
tion of  cream  are  essentially  of  the  same  construction  as 
those  used  for  pasteurizing  skim  milk,  we  shall  here  only 
refer  to  the  description  of  these  which  will  be  found  in  Part 
III  of  this  book. 


PAET  III. 

SKIM-MILK. 


BEFORE  considering  the  factors  which  influence  the 
keeping  quality  of  skim-milk  it  will  be  in  order  to  point 
out  that  there  are  different  kinds  of  skim -milk  of  greatly 
differing  qualities,  and  in  many  respects  of  different  antece- 
dents. These  differences  are  mainly  due  to  the  different 
methods  of  cream  separation  by  which  the  milk  has  been 
obtained. 

SKIM-MILK  FROM  GRAVITY  CREAMING. 

The  skim-milk  obtained  by  the  old  shallow-setting 
system  is  already  sour  when  the  cream  is  skimmed  off,  and 
as  a  rule  it  remains  sour  for  a  sufficiently  long  time  before 
any  other  fermentation  to  all  appearances  occurs.  So 
long  as  the  lactic  acid  is  not  too  strong  in  the  skim-milk 
the  lactic-acid  bacteria  may  thrive  there;  but  after  a 'time 
their  vital  force  is  gradually  weakened  by  the  strong 
acidity  which  they  themselves  have  produced,  and  'to  the 
same  extent  others,  especially  the  butyric-acid  bacteria, 
enter  into  full  activity.  The  latter  have  up  to  this  point 
only  lived  a  torpor-like  existence,  but  they  now  grow  into 
activity;  the  pleasantly  acidulated  taste,  which  is  the  best 

193 


194  MODERN    DAIRY    PRACTICE. 

quality  of  the  skim-milk,  is  lost  and  the  applicability  of  the 
milk  decreased. 

The  length  of  time  in  which  this  milk  will  keep 
slightly  acid  varies  greatly.  I  have  noticed  cases  where 
such  milk  has  kept  evenly  sour  for  several  days,  and  others 
where  it  assumed  a  rancid  taste  within  twenty-four  hours. 
The  different  conditions  to  which  the  milk  has  been  pre- 
viously exposed  will  largely  decide  how  long  the  sample  will 
keep.  These  conditions  exert  the  same  influence  on  the 
skim-milk  as  on  any  other  milk,  and  we  find  that  if  the 
new  milk  has  been  handled  carelessly  the  skim-milk  ob- 
tained from  it  will  possess  a  very  inferior  keeping  quality. 

The  manner  in  which  the  sour  milk  is  kept  has  also 
decided  influence  on  its  keeping  quality.  Proper  clean- 
liness must  above  all  be  observed;  the  acidity  should  not 
be  allowed  to  develop  too  far.  Strong  cooling  or  pasteuri- 
zation need  not  be  applied,  but  the  temperature  should  be 
kept  at  a  point  that  will  allow  the  lactic-acid  fermentation 
to  continue,  but  not  to  develop  excessively.  This  seems  to 
take  place  best  at  60°  F.  The  lactic-acid  bacteria  then 
multiply  easily  (although  not  as  rapidly  as  at  77°  F.),  and 
so  strongly  that  they  may  hold  in  check  the  other  bacteria 
found  in  the  skim-milk.  This  is  easily  accomplished  by 
keeping  the  sour  skim-milk  in  a  light  room  and  in  not  too 
deep  pans,  and  by  stirring  the  milk  occasionally.  By  these 
precautions,  and  by  mixing  some  sour  skim-milk  with  it 
every  day,  it  is  possible  to  keep  such  skim-milk  of  about 
even  acidity  for  several  weeks,  as  I  have  often  seen  done. 

In  the  modern  methods  of  creaming  the  cream  is  always 
removed  in  a  sweet  condition,  and  the  skim-milk  is  also  as 
a  rule  sweet.  The  problem  of  its  keeping  quality  is  there- 
fore entirely  different  from  that  of  sour  skim-milk.  In 


SKIM-MILK.  195 

this  case  we  understand  the  same  by  the  term  "keeping 
quality  "  as  in  case  of  new  milk,  for  which  reason  all  that 
has  been  said  in  regard  to  the  keeping  quality  of  the  latter 
holds  good  also  with  sweet  skim-milk. 

Different  kinds  of  sweet  skim-milk  will  keep  for  a 
longer  or  shorter  time  according  to  the  method  of  creaming 
practised  and  the  treatment  it  receives.  The  skim-milk 
obtained  from  the  Holstein  method  is  often  quite  acid, 
although  it  ought  to  be  sweet.  This  skimmed  milk  being 
often  "blue-soured"  and  of  poor  quality,  it  cannot  be 
expected  to  keep  long,  and  at  farms  where  the  method  is 
used  the  complaint  is  often  made  that  the  skim-milk 
causes  the  calves  to  scour.  In  the  Gussander  method  the 
skim-milk  is  also  reported  not  to  keep  well;  in  the  deep 
setting  system,  on  the  other  hand,  it  keeps  so  much  the 
better.  The  skim-milk  obtained  by  the  ice  method  may 
be  even  model  as  far  as  keeping  quality  goes — i.e.,  if  the 
milk  has  been  properly  handled  previous  to  the  cream- 
ing and  later  on  has  been  treated  in  the  dairy  according  to 
the  strict  directions  of  the  ice  method.  We  have  seen 
that  the  skim-milk  is  not  deprived  of  any  of  its  bacteria  in 
the  ice  method;  all  germs  present  in  the  milk  before  the 
cooling  are  found  in  it  when  they  escape  the  torpor  into 
which  they  are  placed  through  the  cooling.  By  pasteuriz- 
ing the  skim-milk  the  number  and  vital  power  of  the  bac- 
teria found  in  the  same  may  be  diminished,  and  if  it  is  at 
once  properly  cooled  the  advantages  thus  gained  will  be 
retained. 

Separator  Skim-milk. — The  skim-milk  offering  the  best 
guarantee  for  keeping  quality  is,  however,  that  obtained  by 
the  centrifugal  method  of  creaming.  Docent  Fjord  cor- 
rectly stated  in  a  lecture  in  1883  that  separated  milk  must 


196  MODERN   DAIRY   PRACTICE. 

be  considered  the  "  cleanest  of  all  milk."  But  this  purity 
of  the  separator  skim-milk  is  far  greater  and  more  impor- 
tant than  he  suspected  at  the  time.  He  gave  this  opinion 
because  he  saw  the  great  advantage  arising  from  the 
removal  of  the  microscopic  impurities  of  the  milk  by 
means  of  the  centrifugal  force.  It  has  now  further  been 
established  that  separator  skim-milk  contains  fewer  bac- 
teria than  even  the  milk  from  which  it  was  prepared.  The 
data  given  on  page  184  give  decided  evidence  on  this 
point.  Separator  skim-milk  will,  therefore,  keep  better  than 
any  other  not  especially  prepared  milk.  It  is  furthermore 
more  palatable  than  other  skim-milk,  since  it  is  purer  and 
may  be  obtained  in  almost  as  fresh  condition  as  new  milk.* 
The  separation  may  take  place  directly  after  the  milking, 
and  if  the  skim-milk  is  cooled  immediately  after  this  opera- 
tion it  will  keep  well. 

Pasteurization  of  Skim-milk. — The  keeping  quality  of 
the  separator  skim-milk  may  be  further  increased  by  pas- 
teurization and  subsequent  rapid  cooling.  These  opera- 
tions are  especially  essential  if  the  milk  has  become  highly 
infected  by  bacteria  in  the  stable  or  during  the  transporta- 
tion. As  shown  by  the  table  given  on  page  184  not  even 
the  separation  is  sufficient  to  produce  skim-milk  poor  in 
bacteria,  and  it  is  therefore  necessary  to  adopt  further  pre- 
cautions to  maintain  the  keeping  quality  of  the  milk,  for 
which  purpose  pasteurization  and  cooling  are  especially 

*  Fjord  in  Tidsskrift  for  Landokonomi,  1883,  says:  "As  regards 
the  sweetness  of  the  centrifugal  skim-milk  it  may  be  taken  for 
granted  that  every  housewife  will  prefer  a  sweet  milk  poor  in  fat  for 
a  half-soured,  richer  milk,  no  matter  if  the  milk  is  consumed  un- 
boiled, or  if  it  is  to  be  previously  boiled,  by  which  process  the  sour 
milk  is  easily  coagulated." 


SKIM-MILK. 


197 


adapted.  Our  creamery-men  ought  particularly  to  note 
this  fact,  since  the  milk  received  by  them  is  often  highly 
infected  with  bacteria. 

If  further  proof  of  the  importance  of  pasteurization  and 
cooling  of  the  skim-milk  is  needed  I  may  refer  to  the  22d 
Report  of  the  Royal  Danish  Experiment  Station.  The 
results  of  lengthy  practical  investigations  in  this  line,  care- 
fully conducted  by  Mr.  A.  P.  Lunde,  are  published  in  this 
excellent  report  and  form  a  worthy  continuation  of  Fjord's 
experiments.  The  results  present  the  most  striking  proof 
of  the  importance  and  necessity  of  increasing  the  keeping 
quality  of  skim-milk  by  the  operations  mentioned.* 

A  short  explanation  may  be  in  order  concerning  the 
different  pasteurizing  apparatus  and  coolers  at  present  on 

*The  following  summary  of  experiments  in  heating  skimmed 
milk  to  different  temperatures  and  subsequent  cooling,  conducted  by 
Fjord  (1884)  and  Lunde  (1890),  show  that  the  keeping  quality  of 
the  milk  is  directly  dependent  on  the  degree  of  heat  and  of  cooling 
applied.  The  milk  was  cooled  to  12^°  C.  (54°  F.)  in  the  experiments 
of  1884,  and  to  25°  C.  (77°  F.)  in  those  of  1890.  The  figures  given 
represent  the  number  of  hours  during  which  the  skim-railk  could 
stand  boiling. 


No 
Heating 
Applied. 

Skim-milk  Heated  to 

Skim-milk 
Cooled  to 

50°  C. 

(122°  F.) 

60°  C. 
(140»F.) 

65"  C. 

(149°  F.) 

70°  C. 

(158°  F.) 

80«C. 
(176°  F.) 

90°  C. 
(194°  F.) 

1884. 
1890. 

11.8 
5.0 

17.0 
6.9 

27.8 
20.8 

34.8 
28.0 

37.0 
36.9 

40.4 
38.0 

41.2 
41.6 

12i°  C.  (54°  F.). 
25*  C.  (77°  F.). 

(22d  Report  Copenhagen  Experiment  Station,  1891,  p.  35). 
Lunde  (loc.  cit.,  p.  144)  concludes  from  his  numerous  experi- 
ments with  pasteurization  of  skimmed  milk  that  its  keeping  quality 
was  only  slightly  increased  by  the  pasteurization  if  this  was  not  fol- 
lowed by  a  cooling. — W. 


198 


MODERN    DAIRY    PRACTICE. 


the  market.  This  whole  question  of  the  treatment  of  the 
milk  being  a  result  of  the  investigations  of  late  years,  the 
apparatus  bear  in  general  evidence  of  being  first  attempts. 
The  pasteurization  apparatus  most  tried  in  practice  at 
the  present  is  doubtless  the  one  constructed  by  Prof.  Fjord 
in  Denmark,  of  which  a  cut  is  given  below.  The  milk 


FIG.  27. 

reservoir  is  of  tinned  copper  and  is  surrounded  by  a  cover 
of  galvanized  iron,  between  which  the  steam  is  conducted. 
A  stirring  apparatus  resembling  a  churn-pole  is  made  to 


SKIM-MILK. 


199 


200 


MODERN    DAIRY   PRACTICE. 


rotate  in  the  milk-can.  This  keeps  the  milk  in  constant 
motion  and  prevents  it  from  scalding.  Fig.  28  shows  how 
the  apparatus  is  combined  with  a  separator  and  a  cooler; 
the  latter  is  of  a  similar  construction,  as  that  shown  in 
Fig.  26. 

Another  pasteurizing  apparatus  in   the  trade   is  that 
manufactured    by  the   Swedish    Separator    Company  in 


Pro.  29. 

Stockholm  (Fig.  29).  The  apparatus  consists  of  two  copper 
vessels  with  double  walls  and  bottom,  placed  inside  of  one 
another  at  a  distance  of  £— |  of  an  inch.  The  milk,  which  is 
supplied  from  cup  e,  is  heated  between  the  vessels  and  let 
out  at  q,  and  after  finished  pasteurization  at  h.  Steam 
enters  the  vessels  through  the  pipe  b,  which  conducts  it  to 


SKIM -MILK.  201 

the  bottom  of  both  vessels;  the  condensation  water  escapes 
at  c  and  d,  and  after  finished  pasteurization  from  I. 

The  apparatus  is  said  to  work  well,  is  easily  cleaned, 
and  may  easily  be  combined  with  a  cooler.  No  stirring 
contrivance  is  necessary  to  avoid  scalding  of  the  milk,  this 
being  in  motion  during  the  whole  heating  in  a  thin  layer 
between  the  two  warm  surfaces. 

A  pasteurization  apparatus  constructed  by  Bitter  has 
been  adopted  to  some  extent  in  Germany.  It  consists  of  a 
cylinder  holding  about  50  quarts  and  supplied  with  a  cover; 
a  three-centimeter  (l^-inch)  worm  is  placed  in  the  same, 
through  which  the  steam  circulates  and  heats  the  milk 
in  the  cylinder,  which  is  stirred  by  means  of  a  crank. 
Forty  quarts  of  milk  may  be  heated  to  a  temperature  of 
167°  F.  in  fourteen  minutes.  Bitter  has  also  constructed 
hauling-cans  which  are  sterilized  from  the  waste  steam 
and  afterwards  filled  directly  from  the  cylinder,  or  still 
better  directly  from  the  cooler.  The  latter  stands  in  direct 
connection  with  the  pasteurization  apparatus,  and  accord- 
ing to  Bitter's  instructions,  ought  always  to  be  sterilized 
by  steam  before  being  used. 

Besides  the  three  pasteurization  apparatus  briefly  de- 
scribed in  the  preceding,  which  represent  three  different 
types,  a  large  number  of  others  have  been  constructed  dif- 
fering more  or  less  from  these.  As  most  of  these  appa- 
ratus are  new  and  rather  untried,  it  may  be  safest  for  the 
time  being  only  to  buy  them  on  a  guarantee  from  the  man- 
ufacturer or  the  dealer.* 


*For  descriptions  and  illustrations  of  other  apparatus  than 
those  here  mentioned,  see  Weigmann,  "Milchconservirung,"  1893, 
pp.  17-41. -W. 


202  MODERN    DAIRY    PRACTICE. 

Before  leaving  this  subject  it  may  be  well  to  draw  some 
general  conclusions  from  what  has  been  treated  in  the  pre- 
ceding chapter — conclusions  which  may  deserve  attention 
also  of  others  than  dairymen. 

Skim-milk  is  used  as  an  article  of  food  in  the  house- 
hold of  nearly  every  family  in  this  country,  as  well  as  in 
many  public  institutions.  We  often  find  a  prejudice 
against  separator  skim-milk,  however,  and  it  is  therefore 
well  to  inquire  whether  or  not  this  prejudice  is  well 
grounded  and  in  harmony  with  the  facts  given  in  the  pre- 
ceding. 

Separator  skim-milk,  as  we  have  seen,  differs  from 
gravity -process  skim-milk  in  the  following  points : 

1.  It  has  not  been  standing  for  a  long  time  during 
cream  separation. 

2.  It  has  lost  the  disagreeable  macroscopic  impurities  of 
the  milk. 

3.  It  has  fewer  bacteria  than  the  new  milk  from  which 
it  is  prepared  at  the  time  of  separation,  and  will  therefore 
keep  better. 

4.  If  treated  in  the  proper  manner  after  separation  it 
will    also  continue  to  remain    comparatively  free  from 
bacteria. 

Skim-milk  separated  by  gravity  process  has,  on  the 
other  hand,  the  following  shortcomings : 

1.  It  contains  the  greater  portion  of  the  disagreeable 
filth  with  which  it  has  been  mixed  in  the  barn  and  else- 
where, since  straining  only  frees  the  milk  from  the  coarsest 
impurities. 

2.  It  has  been  exposed  to  a  cream  separation  lasting 
twelve  hours  or  more,  when  the  bacteria  in  most  dairies 
have  had  an  opportunity  to  develop. 


SKIM-MILK.  203 

3.  Only  after  pasteurization  and  subsequent  proper 
cooling  will  this  skim-milk  reach  the  high  degree  of  com- 
parative freedom  from  bacteria  possessed  by  the  separator 
skim-milk. 

In  view  of  these  conclusions  we  cannot  but  consider 
the  prejudice  against  separator  skim-milk  for  human  food 
as  unfortunate.  It  is  objected  that  separator  skim- milk 
is  so  entirely  void  of  all  fat  that  it  is  not  fit  for  human 
food.  To  this  it  may  be  answered  that : 

1.  Equally  poor  skim-milk  may  be  obtained  by  the  ice 
method  if  the  milk  is  left  standing  for  several  days. 

2.  Rich  skim-milk  may  also,  if  desired,  be  obtained  by 
means  of  the  centrifuge. 

3.  By  mixing  new  milk  or  cream  with  poor  skim-milk 
any  quality  of  rich  skim-milk  may  be  obtained. 

The  mere  fact  that  the  skim-milk  is  obtained  by  the 
gravity  methods  is  no  guarantee  that  it  is  rich ;  it  is  often 
its  macroscopic  impurities  which  produce  the  impression 
of  richness  (see  p.  139). 


PART  IV. 


BUTTER. 


CHAPTER  I. 


TREATMENT  OF  CREAM  PREVIOUS  TO  THE 
CHURNING. 

IN  describing  the  treatment  of  cream  preparatory  to 
the  churning,  and  in  examining  the  conditions  influencing 
the  keeping  quality  of  the  butter,  we  note  that  the 
different  methods  of  cream  separation  do  not  produce  the 
same  kind  of  cream.  We  thus  distinguish  between  two 
main  groups — the  acid  cream  obtained  from  the  shallow- 
setting  system  and  the  sweet  cream  obtained  in  the  deep 
setting  systems. 

It  is  natural  that  raw  products  so  different  as  these  two 
kinds  of  cream  demand  a  radically  different  treatment,  for 
which  reason  they  ought  to  be  treated  separately.  To 
avoid  repetition  the  treatment  of  sour  cream  from  the 
shallow-setting  system  will  be  explained  after  the  sour 
cream  obtained  by  ripening  of  sweet  cream  has  been  con- 
sidered, and  we  shall  therefore  first  take  up  the  treatment 
of  sweet  cream  preparatory  to  churning. 

204 


TREATMENT   OF   CREAM   PREVIOUS  TO   THE   CHURNING.    205 

Sweet-cream  Butter.  —  The  treatment  which  sweet 
cream  must  undergo  depends,  first  of  all,  upon  how  the 
cream  and  milk  from  which  it  was  made  have  been  pre- 
viously handled,  and  on  the  kind  of  butter  to  be  produced. 
Different  kinds  of  butter  seem  to  require  cream  of  differ- 
ent quality,  and  the  sweet-cream  butter  seem  to  be  spe- 
cially particular  in  this  respect. 

The  cream  used  for  the  manufacture  of  this  kind  of 
butter  must  not  have  undergone  the  least  decomposition, 
since  the  most  important  point  in  this  butter  is  that  its 
taste  has  not  been  changed  by  any  acid  fermentation  in 
the  cream  or  by  other  processes.  Sweet-cream  butter  is 
the  most  delicate,  and  has  the  poorest  keeping  quality  of 
any  kind  of  butter.  In  its  manufacture  the  treatment  of 
both  milk  and  cream  must  therefore,  more  than  ever,  be 
directed  toward  checking  the  growth  of  the  bacteria.  The 
main  precautions  to  be  taken  in  the  manufacture  of  sweet- 
cream  butter  are  as  follows:  rapid  removal  of  the  milk 
from  the  stable  where  the  milking  has  been  done  under  as 
cleanly  conditions  as  possible;  sterilization  of  milk  vessels; 
rapid  cooling  in  a  light  and  clean  room,  or  preferably  cen- 
trifuging,  and  subsequent  strong  cooling  toward  freezing- 
point  (pasteurization  cannot  be  applied,  since  sweet-cream 
butter  easily  assumes  a  cooked  taste);  then  rapid  heating 
to  the  temperature  of  churning,  and  the  most  careful 
churning.  Even  a  partial  neglect  of  these  precautions 
will  tell  on  the  quality  of  the  product  in  one  way  or  an- 
other. On  account  of  the  delicate  nature  of  the  sweet- 
cream  butter  it  has  not  obtained  a  general  sale  on  the  large 
markets. 

Paris  Butter. — In  the  manufacture  of  "  Paris  butter  " 
or  "  St.  Petersburg  butter  "  we  can  reach  a  far  better  keep- 


206  MODERN    DAIRY    PRACTICE. 

ing  quality  than  the  sweet-cream  hutter  can  ever  claim  by 
the  application  of  the  method  adopted  in  the  manufactur- 
ing of  heating  the  cream  to  158°-194°  F.  (70°-90°  0.),  pre- 
ferably to  167°-185°  F.  (75°-85°  C.).  This  is  a  real  and 
thorough  pasteurization,  and  I  need  not  therefore  further 
explain  the  advantages  of  the  system  or  its  manipulation. 
Here  it  may  be  pointed  out  that  the  pasteurization  may  be 
conducted  very  thoroughly;  for  a  cooked  taste  in  the  but- 
ter is  not  objectionable  in  this  case,  but  is,  on  the  contrary, 
a  desideratum.  I  cannot  leave  unmentioned  that  this 
cooked  taste  enables  the  butter-maker  to  hide  all  kinds 
of  faults  in  the  butter  arisen  through  bad  treatment  in  the 
churning  or  working  of  the  butter,  or  through  careless 
handling  of  the  milk  or  cream. 

One  of  the  most  important  conditions  in  the  making  of 
this  butter  is  that  the  cream  be  effectively  cooled  immedi- 
ately after  the  pasteurization  to  a  temperature  below  50°  F. 
The  butter  will  then  be  firm  and  will  keep  well. 

In  order  to  get  rid  of  the  bacteria  more  completely,  I 
have  applied  the  method  of  intermittent  sterilization  (see 
p.  15)  for  the  pasteurization  of  the  cream,  heating  this  two 
or  three  times  to  140°-149°  F.  (60°-65°  C.),  with  cooling 
between  each  heating.  The  last  heating  was  always  con- 
tinued up  to  158°  F.  (70°  C.).  The  result  was  an  extraor- 
dinarily well-keeping  "  Paris  butter."  When  the  tempera- 
ture was  not  raised  above  140°  F.  (60°  C.)  the  first  time, 
and  only  three  heatings  were  made,  the  butter  had  a 
normal  taste,  while  if  the  temperature  was  raised  to  149° 
F.  (65°  C.)  the  first  time  the  butter  possessed  a  somewhat 
too  pronounced  cooked  taste. 

Besides  improving  the  keeping  quality  of  the  butter 
the  pasteurization  of  the  cream  is  beneficial  in  killing 


TREATMENT  OF   CREAM   PREVIOUS   TO   THE   CHURNING.    207 

tubercle  bacilli  as  well  as  other  infectious  bacteria  that  may 
be  found  in  it.  According  to  Bang's  investigations  the 
tubercle  bacilli  in  milk  are  killed  by  heating  to  176°-185° 
F.  (80°-S5°  0.).*  This  occurred  if  the  milk  was  only 
heated  up  to  the  last  temperature  given,  and  not  kept  at 
this  temperature  for  any  length  of  time.  A  temperature 
of  144°  F.  (62°  C.)  made  the  infected  milk  greatly  less 
dangerous,  and  at  162°  F.  (72°  C.)  it  generally  grew  en- 
tirely harmless.  This  matter  is  of  importance,  for  Gas- 
perini  has  directly  proved  that  the  butter  can  contribute 
to  the  spreading  of  tuberculosis.  Even  122  days  after  the 
milk  was  infected  with  tubercle  bacilli  the  butter  made 
from  it  contained  virulent  bacilli  which  killed  animals  in- 
oculated with  it. 

Lafar  also  found  that  spores  of  typhus,  cholera,  and 
tubercle  bacilli  would  retain  their  vitality  for  a  sufficiently 
long  time  in  butter  to  carry  these  diseases  to  living  beings. 

Sour-cream  Butter. — In  the  manufacture  of  sour-cream 
butter,  other  methods  than  those  given  must  be  followed 
in  severa-l  respects.  It  is  here  necessary  that  a  lactic-acid 
fermentation  shall  have  taken  place  in  the  cream. 

As  is  well  known,  there  are  two  different  kinds  of  sour- 
cream  butter  in  the  market,  viz.,  farm  (or  dairy)  butter 
and  creamery  butter.  In  case  of  the  former  kind  the 
lactic-acid  fermentation  has  usually  taken  place  slowly 
during  the  creaming  in  shallow  wooden  pans,  while  in  the 
manufacture  of  the  latter  kind  all  fermentations  were 
checked  by  cooling  during  the  cream  separation,  and  a 
comparatively  rapid  lactic-acid  fermentation  was  started  in 
the  cream  after  the  skimming.  The  lactic-acid  fermenta- 

*  See  foot-note  on  page  158. 


208  MODERN   DAIRY    PRACTICE. 

tion  is  in  the  former  kind  usually  caused  by  bacteria  found 
in  large  numbers  on  the  walls  and  bottom  of  the  pans,  or 
is  started  by  means  of  buttermilk,  sour  milk,  and  skim- 
milk.  No  pure  cultures  are  here  applied;  but  the  bacteria 
happening  to  be  found  in  the  pans  or  the  milk  are  given 
full  liberty  to  produce  their  characteristic  fermentations, 
in  the  hope  that  the  lactic-acid  bacteria  will  be  victorious. 
This  hope  in  some  cases  miscarries — other  fermentations 
occurring  along  with  the  lactic-acid  fermentation,  while 
in  other  cases  this  planless  ripening  yields  surprisingly 
good  results.  As  before  stated,  I  have  thus  at  several 
farms  met  with  buttermilk  obtained  after  ripening  of  such 
spontaneously  soured  cream  which  proved  to  contain  almost 
exclusively  lactic-acid  bacteria. 

The  reason  why  these  samples  of  buttermilk  contained 
practically  pure  cultures  of  lactic-acid  bacteria  doubtless 
lay  in  the  great  cleanliness  and  strict  care  of  which  all  the 
dairy  work  at  these  farms  bore  witness,  as  well  as  in  the 
skill  with  which  the  creaming  and  ripening  process  was 
conducted.  I  have  still  oftener  met  with  ice  or  sep- 
arator creameries  where  practically  pure  cultures  were 
found  in  the  buttermilk. 

The  method  used  in  bacteriological  investigations  for 
obtaining  pure  cultures  originated  with  Pasteur,  who  pub- 
lished his  first  experiments  in  this  line  in  1857.  Succes- 
sive inoculations  are  made  of  mixtures  of  bacteria  in  differ- 
ent samples  of  the  same  substratum  in  order  to  learn 
which  of  the  bacteria  thrive  best  in  the  medium  at  hand. 
If  different  kinds  of  bacteria  are  inoculated  in  a  certain 
medium,  the  organisms  for  whom  this  medium  is  most 
favorable  easily  gain  the  upper  hand  over  the  others. 

If  a  mixture  of  bacteria,  e.g.,  those  found  in  ripened 


TREATMENT   OF    CREAM   PREVIOUS  TO   THE   CHURNING.   209 

cream — is  inoculated  into  sterilized  milk,  certain  ones  will 
soon  gain  superiority  and  produce  their  specific  fermenta- 
tion. If  some  of  the  soured  sample  taken  when  the  fer- 
mentation is  most  active  is  then  inoculated  into  a  new  lot 
of  sterilized  milk  and  the  inoculation  repeated  in  the  same 
way,  cultures  of  a  certain  bacteria  are  after  awhile  obtained 
which  in  most  cases  may  be  considered  pure.  The  sub- 
stratum has  then  offered  so  favorable  conditions  of  life  to 
this  kind  of  bacteria  that  it  has  been  able  to  suppress  all 
others.  In  this  manner  I  once  obtained  a  pure  culture 
of  a  lactic-acid  bacteria  from  a  very  impure  sample  of 
milk.* 

How  do  these  conditions  occcur  in  practice  in  the 
ripening  cream  in  shallow  pans  ?  In  the  first  place  the 
lactic-acid  bacteria  are  favored  in  every  way  in  these,  milk 
being  the  most  favorable  nutritive  medium  imaginable. 
Secondly,  souring  material  is  transferred  partly  uncon- 
sciously (the  wall  and  bottom  of  the  pan),  partly  con- 
sciously by  addition  of  sour  milk  in  which  the  fermentation 
is  at  its  height.  It  will  be  seen  that  there  are  here  many 
points  of  similarity  with  the  method  applied  in  laboratories 
for  production  of  pure  cultures.  Conscious  infection  by 
means  of  sour  milk  does  not  often  take  place  in  farm- 
dairying,  and  is  only  resorted  to  when  the  unconscious 
infection  has  proved  insufficient.  I  have,  however,  found 
places  in  Savolaks  where  such  inoculation  of  acid  bacteria 
has  been  the  rule  and  was  applied  almost  daily.  This  in- 
fection in  one  place  occurred  by  dipping  the  wooden  spoon 
used  in  skimming  the  sour-milk  pans  into  the  pan  con- 

*  "  Studien  tiber  die  Zersetzungen  der  Milch,"  in  Fortschritie  der 
Medicin,  1889,  pp.  122,  123. 


210  MODERN"    DAIRY    PRACTICE. 

taining  sweet  milk.*  Thanks  to  this  manner  of  procedure, 
the  souring  took  place  more  rapidly. 

In  the  unconscious  infection  of  fermentation-starters, 
the  cause  usually  lies  in  the  fact  that  the  milk-pans  used 
for  creaming  have  not  been  sufficiently  cleaned.  The 
result,  however,  in  this  case  must  evidently  be  more  un- 
certain. Strange  to  say,  we  rarely  find  other  than  lactic- 
acid  bacteria  in  excessive  numbers  in  sour  milk  at  our 
farms.  The  reason  is  doubtless  that  these  bacteria  are  not 
checked  as  strongly  in  their  development  as  others,  the 
milk-pans  being  placed  outdoors  in  the  sun,  dried  and 
aired,  to  which  treatment  the  putrefactive  bacteria  are 
very  especially  sensitive.  If  the  pans  be  thoroughly  sun- 
baked they  become  wholly  sterile,  as  we  saw  before,  and 
the  souring  of  the  milk  has  then  to  be  started  by  inocula- 
tion with  sour  milk. 

The  inoculated  milk  is  mixed  with  all  kinds  of  bacteria, 
and  the  ripening  is  not  therefore  always  successful.  One 
result  of  this  fact  is  that  farm  butter  is  so  much  poorer 
in  winter,  when  milk  is  produced  in  the  stable.  Com- 
paratively good  pure  cultures  may,  however,  be  obtained 
under  the  primitive  conditions  present  in  the  manufac- 
ture of  farm  butter.  If  an  effort  is  made  to  improve 
these  conditions  by  introducing  greater  cleanliness  in 
stable  and  dairy,  and  by  increasing  the  knowledge  of  the 
principles  of  dairying  among  farmers,  the  result  ought  to 
be  still  better.  If,  for  instance,  the  milk  is  pasteurized 
before  being  creamed,  we  should  soon  find  that  the  souring 
will  always  take  place  in  a  proper  manner  also  in  the 
shallow  setting  system. 

*  At  farms  in  Norway  this  inoculation  is  often  effected  by  plac- 
ing a  little  pure  sour  milk  at  the  bottom  of  the  milk-pans.— W. 


TREATMENT   OF   CREAM   PREVIOUS   TO   THE   CHURNING.   211 

Adding  sour  buttermilk,  etc.,  to  cream  is  also  practised 
in  the  ripening  of  cream  from  modern  methods  of  cream- 
ing; and  here  it  will  happen  oftener  that  pure  cultures  of 
a  single  bacterium  are  obtained.  The  better  conditions  at 
the  creameries  and  dairies  using  these  methods  tend  to 
bring  about  this  result;  and  the  application  of  accessories, 
as  pasteurization  of  the  cream,  etc.,  would  clearly  still 
further  forward  it. 

It  is  by  no  means  an  easy  matter  to  properly  conduct 
the  ripening  of  the  cream  under  differing  conditions  of 
temperature  and  facilities;  it  requires  great  care  and 
power  of  observation  as  well  as  a  good  store  of  knowledge 
on  part  of  the  butter-maker.  The  ripening  of  the  cream 
has  such  a  decisive  influence  on  the  qualities  of  the  butter 
that  cream  of  the  best  quality  may  be  entirely  spoilt  by 
careless  ripening.  But,  on  the  other  hand-,  a  proper  ripen- 
ing cannot  possibly  be  conducted  in  cream  poorly  cared 
for  and  containing  a  large  number  of  injurious  bacteria. 
The  quality  of  the  butter  depends  more  than  is  generally 
acknowledged  on  the  manner  in  which  the  milk,  the 
cream,  and  butter  have  been  treated,  and  above  all,  on 
the  ripening  of  the  cream.  Martens  said  as  early  as 
1869:  "-Although  other  conditions,  as  the  winter  feeding, 
the  pasture,  the  milk-cellar,  etc.,  greatly  influence  the  qual- 
ity of  the  butter,  these  factors  very  often  get  the  blame 
for  faults  originating  through  carelessness  in  the  treat- 
ment." 

The  first  condition  for  obtaining  a  proper  ripening  is 
that  the  raw  material  shall  be  good.  If  the  quality  of  the 
cream  is  uncertain  it  is  always  safest  to  pasteurize  it  before 
ripening!  If  this  operation  be  well  done,  and  the  cream 
be  rapidly  cooled  immediately  after  the  pasteurization,  the 


212  MODERN   DAIRY   PRACTICE. 

sour-cream  butter  will  not,  as  we  saw  before,  have  a  cooked 
taste. 

The  Danish  experiments  spoken  of  on  page  197  show 
conclusively  that  pasteurization  properly  conducted  never 
injures  or  diminishes  the  fine  quality  of  the  butter,  but,  on 
the  other  hand,  is  very  beneficial  to  the  same.  The  butter 
will  keep  better  at  the  same  time,  as  bad  flavors  and  taste 
are  prevented  from  appearing  in  it.  The  yield  of  butter 
obtained  will  be  somewhat  lowered,  partly  because  the 
buttermilk  will  be  richer,  partly  because  the  butter  will 
contain  less  water;*  but  this  decrease  is  in  reality  insig- 

*  As  an  average  of  51  trials  with  pasteurized  and  non-pasteurized 
cream,  Lunde  obtained  3.73  Ibs.  of  butter  from  100  Ibs.  of  milk  in 
case  of  ordinary  cream,  and  3.68  Ibs.  in  case  of  pasteurized  cream, 
or  a  loss  of  1.3  per  cent. 

He  obtained  the  following  average  results  as  regards  the  water 
content  of  the  butter  made  by  the  various  processes: 

Normal  cream  (15  trials) 14.35  per  cent. 

Pasteurized  cream    "      13.74        " 

milk      "      12.85 

Normal  cream  (22  trials) 14. 17  per  cent. 

Pasteurized  milk    "       13.03 

The  buttermilk  contained  on  an  average  for  all  experiments  the 
following  percentages  of  fat: 

Normal  cream..  33  per  cent. 

Cream  pasteurized 37       " 

Milk  pasteurized 55       " 

See  also  Berg,  Nordisk  Mejeri-Tidn,  9,  p.  126;  Exp.  Sta.  Record 
5,  p.  1025. 

Lunde  (22d  Report  Copenhagen  Experiment  Station,  1891,  p.  110) 
summarizes  his  work  on  pasteurization  as  follows:  "  If  a  creamery 
works  under  normal  conditions  and  makes  first-class  butter,  it  will 


TREATMENT   OF   CREAM    PREVIOUS   TO   THE   CHURXIHG.   213 

nificant,  especially  since  a  lower  water  content  must  be 
considered  a  direct  advantage.  The  lower  percentage  of 
water  has  also  in  a  measure  the  effect  of  making  this 
butter  keep  better  than  butter  from  non-pasteurized  cream. 

The  second  condition  for  a  good  ripening  of  the  cream 
is  that  the  butter-maker  shall  be  well  informed  on  dairy  mat 
ters  and  shall  watch  the  process  himself.  He  should  be 
present  from  the  beginning  to  the  end  every  time  the  starter 
is  prepared;  should  be  present  when  the  ripening  of  the 
cream  is  begun;  should  carefully  follow  the  whole  process, 
and  when  it  is  done,  examine  the  sourness  of  the  cream. 
Carelessness  in  the  ripening  at  once  stamps  the  butter- 
maker  as  incapable. 

Ripening  Room  and  Vessels. — To  secure  a  proper  ripen- 
ing of  the  cream  the  creamery  should  contain  a  separate 
ripening-room,  as  it  is  otherwise  very  difficult  to  produce 
a  good  fermentation.  In  many  places  the  ripening-can 
(or  vat)  is  placed  in  the  separator-room.  This  practice  is 
reprehensible,  among  other  reasons  because  an  even  tem- 
perature cannot  possibly  be  maintained  there,  and  neither 
can  the  atmosphere  be  kept  properly  dry;  the  strict  clean- 
lines  necessary  where  the  ripening-vat  is  placed  cannot 
possibly  be  observed  in  this  room.  The  ripening-room 
should  be  well  isolated  from  dwelling-rooms  and  other 
creamery-rooms.  It  should  not  be  directly  connected  with 

hardly,  according  to  our  experiments,  pay  to  introduce  pasteuriza- 
tion, if  a  somewhat  higher  price  than  before  be  not  obtained  on 
account  of  the  better  product.  If,  on  the  other  hand,  a  creamery 
has  difficulties  in  making  firstjdass  butter,  so  that  the  price  is  always 
discounted  because  this  or  that  shipment  was  of  inferior  quality, 
pasteurization  will  as  a  rule  be  an  efficient  means  of  removing  the 
trouble  and  again  obtaining  the  previous  price." — W. 


214  MODERN    DAIRY    PRACTICE. 

the  cheese-room  or  curing-rooms,  for  the  fermentation 
processes  favored  in  these  are  of  a  wholly  different  nature 
and  inimical  to  the  changes  to  be  brought  about  in  the 
ripening  of  the  cream.  It  is  also  evident  that  the  ripen- 
ing-room ought  not  to  serve  as  a  passage-room,  and  that  it 
must  be  free  from  draught  and  equipped  so  that  an  ex- 
treme cleanliness  may  exist  throughout.  It  must  be  well 
ventilated  and  kept  at  an  even  temperature  (from  50°-65° 
F.)  The  air  should  be  dry,  as  it  is  otherwise  very  difficult 
to  prevent  all  kinds  of  fermentation  from  arising. 

The  room  must,  of  course,  be  provided  with  large  win- 
dows, so  that  light  and  sunshine  may  enter  into  it.  It 
need  not  be  very  large  and  must  not  be  used  for  any  other 
purpose — except,  perhaps,  for  storing  of  butter  ready  for 
shipment. 

Wooden  cans  or  tin  vats  are  used  for  ripening  cream. 
At  the  present  the  former  are  most  used  in  Finnish  cream- 
eries; and  if  manufactured  of  hard,  close-grained  oak,  they 
may  without  difficulty  be  used  for  some  time,  as  they  can 
then  be  easily  and  thoroughly  cleaned  and  sterilized;  but 
if  old  and  made  of  soft,  loose  wood,  they  have  a  very 
deleterious  influence  on  the  ripening,  as  they  cannot  be 
properly  cleaned  even  by  steaming,  and  the  result  is  that 
all  kinds  of  bacteria  lodge  in  them  which  may  give 
rise  to  faulty  ripening.  In  my  opinion  the  ripening-vats 
prepared  from  tin,  or  tinned  copper,  are  always  to  be  pre- 
ferred, as  they  may  easily  be  kept  clean  and  sterile.  Metal 
vessels  are  sometimes  objected  to  on  account  of  being  good 
conductors  of  heat;  but  if  a  proper  ripening-room  the 
temperature  of  which  can  be  regulated  is  available,  this 
objection  will  be  of  no  importance.  If  such  a  room  can- 
not be  obtained,  an  even  temperature  of  the  cream  may 


TREATMENT  OF   CREAM    PREVIOUS   TO   THE   CHURNING.    215 

easily  be  obtained  by  enclosing  the  ripening- vessel  in  wood, 
hay  mattresses,  etc. 

In  the  creameries  of  North  Germany  the  ripening 
usually  takes  place  in  small  tin  vessels  placed  in  water- 
basins,  the  temperature  of  which  is  regulated  by  means 
of  steam  or  ice.  In  many  respects  this  is  a  very  prac- 
tical method;  but  it  has  the  disadvantage  that  a  good 
deal  of  moisture  is  introduced  into  the  ripening-room,  so 
that  it  becomes  very  difficult  and  almost  impossible  to 
keep  the  room  free  from  colonies  of  mold  and  bacteria. 

The  Ripening  Process.  —  In  many  places  abroad — for 
instance  in  Germany — the  contents  of  the  ripening-vat 
are  left  to  sour,  without  the  addition  of  any  starter,  as  in 
case  of  the  old  shallow-setting  system.  This  method 
is,  however,  too  slow  and  uncertain,  and  the  application  of 
a  separate  acid  starter  is  therefore  always  to  be  recom- 
mended. We  must  carefully  watch  so  that  the  cream  is 
not  contaminated  or  mixed  through  the  starter  with  a 
fluid  containing  faulty  fermentations.  The  qualities  of 
the  starter  must  therefore  be  daily  tested  by  taste  and 
odor,  and  the  progress  of  the  ripening  process  be  watched 
by  repeated  careful  observations. 

Acid  Starter. — At  our  creameries  three  different  kinds 
of  starters  are  generally  used  at  the  present,  viz. :  (1)  butter- 
milk from  the  last  churning;  (2)  ripened  cream;  (3)  butter- 
milk from  another  creamery.  The  well-known  Danish 
dairy  instructor,  Boggild,  treated  this  topic  in  a  lecture  de- 
livered in  Odense  in  1890.  The  following  description  and 
discussion  of  the  ripening  process  is  taken  from  the  lecture  : 

1.  Buttermilk  Acid  Starter. — "  There  is  no  lack  of  ex- 
amples that  older,  well-conducted  creameries  have  used 
buttermilk  as  starter  during  a  series  of  years;  but  i.  would 


216  MODERN   DAIRY    PRACTICE. 

be  incorrect  to  conclude  from  this  that  such  a  method  of 
procedure  is  applicable  under  all  conditions,  for  we  have 
learned  by  experience  that  ripening  faults  may  be  trans- 
ferred from  one  lot  of  cream  to  another  by  the  applica- 
tion of  buttermilk,  and  may  even  be  increasing  until 
the  method  of  ripening  is  changed.  The  application  of 
buttermilk  from  the  previous  churning  can  therefore  only 
be  recommended  as  long  as  the  ripening  process  occurs  in 
the  proper  manner. 

Sour  cream  from  the  mess  ready  for  churning  is  used 
in  place  of  buttermilk  in  some  creameries.  This  has  the 
same  advantage  and  the  same  danger  as  the  use  of  butter- 
milk, and  is  only  to  be  preferred  where  there  is  reason  to 
suspect  that  injurious  micro-organisms  or  other  impuri- 
ties have  been  added  in  the  churning  or  the  washing-down 
of  the  cream.  Both  buttermilk,  cream,  or  any  other  kind 
of  starter  used  must  be  kept  at  a  low  temperature  from 
the  time  it  is  ready  and  till  it  is  to  be  used,  so  that  it  does 
not  become  damaged. 

2.  New  MM  Acid  Starter. — The  application  of  new 
acid  starter  is  of  but  recent  origin;  it  was  previously 
prepared  from  a  mixture  of  water  and  fresh  milk,  but 
it  is  now  generally  made  from  cream,  fresh  milk,  or 
partly  skimmed  milk.  A  suitable  quantity  of  any  of  these 
liquids  is  heated  and  kept  at  a  temperature  most  favorable 
to  the  development  of  the  bacteria  desired  for  the  production 
of  butter;  the  result  of  the  application  of  the  new  starter 
depends  largely  on  the  success  obtained  in  this  process. 

The  object  sought  in  using  a  new  starter  in  place  of 
buttermilk  is  to  improve  the  ripening  process.  It  must 
therefore  be  an  invariable  rule  to  examine  it  carefully  as 
to  appearance,  odor,  and  taste,  and  to  compare  it  with  the 


TREATMENT   OF   CREAM    PREVIOUS   TO   THE   CHURNING.    217 

buttermilk.  If  the  buttermilk  is  better  than  the  new 
starter,  the  former  should  be  used.  As  cream  differs  from 
milk  only  in  its  greater  fat  content,  and  as  fat  does  not 
play  any  part  in  the  nutrition  of  the  lactic-acid  bacteria, 
there  is  no  reason  to  prefer  cream  for  milk  as  a  starter. 
Even  if  the  cream  does  not  give  a  proper  new  starter  it  is 
generally  used  anyway,  as  it  represents  a  certain  quantity 
of  butter,  and  is  not  therefore  fed  to  the  hogs  ;  neither  is 
it  churned  separately,  but  is  used  as  starter  on  the  suppo- 
sition that  it  is  as  it  ought  to  be. 

On  the  basis  of  experience  gained  at  Danish  dairies 
creamery-men  are  advised  always  to  prepare  new  starter, 
to  compare  it  with  the  buttermilk,  and  to  apply  the  one 
that  proves  the  better.  The  milk  best  adapted  to  prepara- 
tion of  starter  should  be  found  by  comparative  trials  with 
the  milk  from  different  patrons.  The  patron  furnishing 
this  milk  should  then  be  asked  to  send  the  milk  from  only 
fresh-milking,  well-fed  cows  in  a  separate  can;  and  this 
should  either  be  sent  to  the  creamery  while  still  warm  or 
subjected  to  a  careful  cooling  on  the  farm.  Immediately 
on  arrival  of  the  milk  at  the  creamery  the  butter-maker 
should  place  it  in  one  or  two  common  cylindrical  milk- 
cans  previously  well  cleaned  with  soda  or  lime  and  scalded 
with  boiling  water;  the  milk  is  then  cooled  as  rapidly  as 
possible  in  ice  or  cold  water.  A  layer  of  cream  will  form 
during  the  forenoon,  and  this  is  then  removed  with  an 
ordinary  skimmer  and  poured  into  the  sweet  cream  from 
the  centrifuge.  The  partly-skimmed  milk  is  used  for 
preparation  of  starter.*  The  milk  is  now  to  be  heated, 

*In  my  opinion  separator  skim-milk  from  a  well-conducted 
farm  is  to  be  preferred  for  such  sweet,  partly-skimmed  milk. — 
G.  G. 


218  MODERN    DAIRY    PRACTICE. 

which  may  best  be  effected  by  lowering  the  milk-can  into 
hot  water,  while  the  milk  is  continually  stirred  by  means 
of  a  galvanized-iron  rod  supplied  with  a  round  disk.  This 
as  well  as  the  milk-can  and  skimmer  must  of  course  have 
been  thoroughly  cleaned. 

At  different  places  and  at  different  seasons  the  milk 
must  be  heated  to  a  temperature  of  77°-95°  F.  (25°-35°  C.) 
to  become  evenly  sour  in  the  course  of  eighteen  to  twenty 
hours.  The  exact  temperature  required  is  determined  by 
experiment.  When  the  correct  temperature  has  been 
reached,  the  milk-can  is  carefully  placed,  so  that  none  of 
the  contents  is  spilled,  into  a  barrel  filled  with  hay.  The 
can  should  be  covered  with  a  clean  cloth,  on  which  a  neat 
hay  mattress  is  put;  the  milk  may  now  be  left  alone  until 
the  next  day.  As  soon  as  the  work  begins  in  the  morning 
the  butter-maker  should  examine  the  starter,  for  the  ripen- 
ing process  may  be  finished.  This  may  conveniently  be 
done  by  placing  the  vessel  in  cold  water  when  the  milk 
becomes  evenly  sour.  In  the  majority  of  creameries  it  is 
most  convenient  to  have  the  acid  ready  at  8  to  10  A.M. 
The  upper  inch  layer  of  the  milk  is  removed  with  a  skim- 
mer, as  it  sometimes  is  less  palatable  than  the  rest  of  the 
acid.  The  starter  is  then  mixed  with  the  stirring-rod  and 
placed  in  cold  water  until  used. 

The  new  starter  does  not  usually  taste  as  sour  as  the 
buttermilk,  and  a  somewhat  larger  quantity  must  there- 
fore be  used  of  it.  As  a  disadvantage  in  the  method  may 
be  mentioned  that  the  souring  does  not  always  progress  in 
the  same  manner,  so  that  the  butter  on  separate  days  of 
even  the  same  week  may  prove  of  different  quality,  while 
an  even  quality  of  butter  is  easily  gained  by  using  a  butter- 
milk starter. 


TREATMENT  OF   CREAM   PREVIOUS   TO  THE   CHURNING.   219 

The  use  of  a  new  starter  is  to  be  recommended  when 
the  quality  of  the  butter  is  deteriorating  or  is  unsatis- 
factory, and  above  all  when  milk  varying  in  freshness, 
purity,  and  general  qualities  is  sent  to  the  creamery. 

Where  the  quality  of  the  butter  is  not  satisfactory,  and 
where  it  also  proves  difficult  or  impossible  to  prepare  good 
new  acid,  it  will  be  necessary  to  apply  buttermilk  from 
another  creamery. 

3.  Buttermilk  from  Another  Creamery  as  Starter. — 
This  should  of  course  be  obtained  only  from  a  creamery 
where  the  butter  is  good,  and  where  the  ripening  is  suc- 
cessfully conducted  at  the  time.  The  practice  of  using 
buttermilk  from  another  creamery  is  very  old,  and  has 
especially  been  used  in  places  where  proper  churning  has 
been  conducted  under  great  difficulties,  and  where  the 
cream  has  not  soured  evenly,  but  has  remained  thin  and 
turned  bitter  and  "off  flavor."  However  simple  this 
remedy  may  seem  it  has  not  often  been  resorted  to— doubt- 
less because  butter-makers  have  considered  it  a  reflection 
on  their  ability  not  to  get  out  of  the  difficulty  by  their 
own  efforts.  The  practice  seems,  however,  now  to  be  more 
generally  followed  as  the  great  importance  of  the  ripening 
of  the  cream  for  the  quality  of  the  butter  is  better  under- 
stood. With  the  experience  of  late  years  we  may  say  that 
in  some  cases  it  is  a  sign  of  ability  and  care  on  part  of  the 
butter-maker  rather  than  the  other  way,  if  he  tries  to  ob- 
tain a  good  starter  from  another  source  when  his  own  has 
for  a  long  time  proved  unsatisfactory. 

It  has  happened  in  some  cases  that  a  butter-maker  has 
succeeded  in  getting  the  ripening  process  in  proper  order 
by  a  single  application  of  good  buttermilk  from  another 
creamery — good  results  having  later  been  obtained  by  ap- 


220  MODERN    DAIRY    PRACTICE. 

plying  buttermilk  from  previous  churnings;  but  there  are 
plenty  of  examples  that  the  difficulty  is  not  always  as 
easily  adjusted,  the  ripened  cream  after  some  days  again 
being  of  the  same  undesirable  quality  as  before.  To  coun- 
teract this  it  has  long  in  all  such  cases  been  a  universal 
remedy  to  make  a  general  housecleaning.  The  ripening- 
vat,  churn,  and  other  wooden  utensils  are  carried  out  in 
the  open  air  for  some  days;  the  creamery-rooms  are  white- 
washed, etc.  This  method  of  procedure  is  doubtless  both 
practical,  correct,  and  necessary;  but  when  it  proves  in- 
sufficient the  attention  must  also  be  directed  toward  the 
other  side  of  the  subject,  and  an  especially  good  starter 
must  be  provided  for  several  days  ahead.  This  may  be 
secured  by  obtaining  good  buttermilk  daily  from  another 
creamery,  but  if  the  distance  is  too  great,  a  culture  of  the 
bacteria  of  the  buttermilk  obtained  may  be  carefully  kept 
and  a  portion  of  the  same  used  daily  as  a  starter." 

Pure-culture  Acid  Starters. — By  the  preceding  meth- 
ods of  securing  a  good  acid  starter  much  is,  however,  left 
at  a  venture.  We  do  not  know  to  which  lactic-acid  bac- 
teria the  successful  outcome  is  due;  and  neither  are  we 
certain  if  the  cream  is  not  infected  by  injurious  bacteria 
from  the  starter.  To  avoid  this  a  new  method  of  prepar- 
ing the  starter  has  been  introduced  in  some  foreign  cream- 
eries during  the  last  couple  of  years,  according  to  the 
principle  which  has  proved  of  such  great  benefit  to  the 
fermentation  industries,  notably  the  brewing  industry. 
As  long  as  yeast  containing  fungi  and  bacteria  of  all 
kinds  was  used  in  the  manufacture  of  beer  there  was  no 
certainty  of  a  successful  fermentation.  A  yeast  fungus 
sometimes  obtained  the  superiority,  a  bacterium  another 
time,  and  the  result  was  therefore  often  different  from 


TREATMENT   OF   CREAM   PREVIOUS  TO   THE   CHURNING.    221 

what  was  wanted;  the  beer  might  turn  bitter,  be  "off 
flavor,"  etc.,  although  the  raw  products  used  were  of  the 
very  best  quality.  Until  lately  we  were  placed  in  the  same 
difficulty  in  the  fermentation  industry  called  the  manu- 
facture of  sour-cream  butter.  The  composition  of  the 
starter  used  is  not  known,  and  it  perhaps  contains  a  large 
number  of  injurious  bacteria.  Although  the  quality  of 
the  cream  was  excellent,  a  bitter,  oily,  turnipy  or  other 
kinds  of  diseased  butter  may  have  been  obtained  owing  to 
the  introduction  of  injurious  bacteria  into  the  cream  from 
the  starter.  The  effort  has  perhaps  been  made  to  produce 
good  milk,  to  handle  it  properly  throughout,  to  take  good 
care  of  it  during  the  transportation  to  the  creamery,  to 
care  for  it  there  according  to  all  the  rules  of  the  art,  to  cool, 
separate  and  pasteurize  it — a  relatively  germ-free  cream 
being  thus  obtained;  and  after  all  this  the  delicate  product 
is  calmly  mixed  with  a  fluid  the  qualities  of  which  are 
only  partially  known,  and  all  preceding  efforts  may  thus 
be  overthrown.  By  a  good  deal  of  practice  and  experi- 
ence the  ripening  may  certainly  be  successfully  conducted 
in  this  way.  A  Danish  butter-maker  has  thus,  as  I  recently 
learned,  been  using  the  same  kind  of  starter  for  fourteen 
years  without  having  ever  had  a  faulty  ripening.  In  the 
same  way  experienced  brewers  were  able  to  make  good 
beer  also  before  the  introduction  of  pure  cultures;  but 
there  could  be  no  certainty  of  a  good,  uniform,  and  well- 
keeping  product  until  the  adoption  of  the  latter  process. 

Butter-makers  cannot  prepare  such  a  starter  them- 
selves, however,  but  are  obliged  to  turn  to  a  bacteriological 
laboratory  that  can  furnish  them  with  pure  cultures  of 
lactic-acid  bacteria.  We  shall  return  to  the  pure  cultures 
of  these  bacteria  at  the  end  of  this  chapter  in  connection 


222  MODERN   DAIRY   PRACTICE. 

with  a  further  description  of  the  nature  and  character- 
istics of  the  different  lactic-acid  bacteria. 

The  methods  of  applying  these  pure  cultures  in  the 
creamery  business  were  vague  and  uncertain  until  of  late; 
the  solution  of  the  problem  was  only  a  couple  of  years 
ago  in  its  first  stage  of  development. 

Storch  (Copenhagen)  recommends  the  following  method 
of  procedure  for  the  application  of  pure  cultures :  "  The 
starter  is  to  be  prepared  daily  by  means  of  a  pure 
culture;  the  latter  may  best  be  supplied  to  the  creamery 
in  especially-arranged  vessels,  from  which  it  may  be 
drawn  in  small  portions  without  danger  of  contamination ; 
the  creamery-man  adds  a  sufficient  quantity  to  as  much 
new  milk  (or  perhaps  preferably  separator  skim-milk)  as 
the  creamery  is  in  the  habit  of  using  for  a  starter.  Before 
adding  the  pure  culture  the  milk  is  heated  above  158°  F., 
and  at  once  cooled  to  the  temperature  at  which  the  ripen- 
ing will  take  place  safest  and  quickest.  It  is  possible  that 
another  heating  of  the  milk  to  158°  F.  after  a  day's  in- 
terval will  be  found  necessary.  When  sufficiently  acid 
and  completely  curdled  this  milk  is  ready  to  be  used  as  a 
starter." 

Weigmann  (Kiel)  gives  the  following  method:  "The 
pure  culture  is  to  be  ordered  from  a  bacteriological  labora- 
tory; full-skimmed  separator  skim-milk  is  used  in  prepar- 
ing the  starter.  The  bacteria  found  in  the  same  are 
weakened  or  partially  destroyed  by  cooling  or  heating;  if 
cooling  be  applied  it  must  be  very  effective  (37°-30°  F.).  It 
is,  however,  better  to  heat  the  milk  to  140°  F.,  cooling  it  at 
once  afterwards  to  68°-77°  F.  A  portion  of  the  pure  culture 
is  then  added,  at  the  same  time  stirring  the  milk  carefully. 
The  starter  will  be  ready  the  following  day,  and  should  be 


TREATMENT  OF   CREAM   PREVIOUS  TO   THE   CHURNING.    223 

renewed  every  day  by  adding  sweet  skim-milk.  When  a 
disease  of  the  butter  is  being  fought,  pure  cultures  must 
for  some  time  be  applied  every  day  for  preparing  the 
starter;  otherwise  a  fortnightly  application  of  pure  cultures 
will  suffice." 

In  my  latest  experiments  with  pure  cultures  in  practical 
dairying  I  have  used  the  following  method  of  procedure : 
Morning  milk  from  a  well-kept  farm  was  separated  as  soon 
as  it  came  to  the  creamery.  Part  of  the  skim-milk  obtained 
was  carefully  pasteurized;*  then  cooled  to  77°-82°  F.  (25°- 
28°  C.),  and  the  pure  culture  added.  The  temperature  was 
not  lowered  below  68°  F.,  and  the  milk,  which  was  covered 
by  a  clean  cloth  during  the  whole  time,  was  therefore 
curdled  as  early  as  the  afternoon  of  the  same  day.  The 
cream  separated  in  the  morning  was  pasteurized  (at  158°  F.) 
and  cooled  to  about  39°  F.  It  was  kept  at  this  low  tem- 
perature for  at  least  six  hours;  but  perferably  until  the 
evening,  being  occasionally  stirred.  At  about  6  P.M.  it  was 
heated  to  73°  F.,  the  starter  was  added,  and  the  cream-can 
then  kept  wrapped  in  a  hay  mattress  at  ordinary  room 
temperature  (64°  F.).  The  cream  was  stirred  at  least  twice 
during  the  evening,  with  an  hour's  interval.  It  was  usually 
properly  acid  and  uniform  the  next  forenoon,  and  after 
some  cooling  was  poured  into  the  churn.f 

*This  milk  may  safely  be  heated  to  185°-194°  F.  (85°-90°C.). 
Even  if  the  starter  has  a  cooked  taste,  the  cream  ripened  by  it  will 
not  according  to  my  experience  have  this  taste  unless  extraordinarily 
large  proportions  of  starter  are  used. 

fThe  starter  used  by  C.  O.  Jensen  in  his  experiments  was  pre- 
pared in  the  following  manner,  according  to  his  own  description : 
"200-600  cc.  (about  7-20  oz.)  of  milk  was  drawn  from  the  cow, 
the  udder  and  teats  having  been  washed  with  a  corrosive-sublimate 
solution  (1.1000) ;  the  teats  were  then  wiped  with  a  sleamed  towel, 


MODERN   DAIRY   PRACTICE. 

The  question  of  how  often  the  new  starter  should  be 
prepared  from  the  pure  culture  cannot  as  a  matter  of 
course  be  answered  so  as  to  apply  to  all  conditions,  as  these 
vary  greatly  at  different  creameries.  The  only  rule  that  can 
be  given  on  this  point  is  to  use  it  as  often  as  it  proves 
necessary.  The  new  starter  is  propagated  in  the  usual 
way,  separated  and  pasteurized  skim-milk  obtained  from 
new  milk  drawn  and  treated  throughout  with  the  most 
minute  care  being  always  used. 

The  new  starter  must  be  watched  to  prevent  the  fer- 
mentation from  proceeding  too  far,  lest  the  acidity  grow  too 
strong  for  the  lactic-acid  bacteria,  thereby  offering  other  bac- 
teria— e.g.,  the  butyric-acid  starters — favorable  conditions 
of  life.  According  to  my  experiments  this  stage  will  occur 
when  the  cream  contains  about  .85  per  cent  of  lactic  acid — 
a  degree  of  acidity  which  but  slightly  exceeds  that  usually 

and  my  hands  were  also  washed  with  sublimate  solution  and  wiped. 
The  milk  was  drawn  directly  into  a  sterile  flask  provided  with  a 
cotton  plug,  through  which  a  piece  of  glass  tubing  about  one  half 
inch  wide  and  three  to  four  inches  long  was  placed  ;  the  latter  was 
also  closed  with  a  small  cotton  plug.  This  plug  was  removed  in 
milking,  and  the  narrow  tube  was  after  the  milking  again  closed  with 
the  plug.  As  a  still  further  precaution  this  milk  was  heated  in  the 
flask  up  to  158°  F.  (70°  0.)  for  ten  minutes  and  rapidly  cooled  to 
about  77°  F.  (25°  C.).  The  seeding  with  the  lactic-acid  bacteria  was 
done  by  introducing  a  recently-ignited  capillary  glass  tube  into  the 
agar-agar  culture  and  placing  it  in  the  milk  through  the  glass  tube  in 
the  cotton  plug.  Treated  with  sufficient  care  the  milk  was  never  con- 
taminated, which  fact  was  always  directly  ascertained.  The  inocu- 
lated milk  was  left  standing  at  77°  F.  (25°  C.),  and  always  soured 
evenly  in  the  course  of  16-20  hours.  From  this  soured  milk  agar- 
gelatine  cultures  were  made,  which  in  their  turn  were  used  the  next 
day  for  preparing  the  new  starter. 


TREATMENT   OF    CREAM    PREVIOUS   TO   THE   CHURNING.    225 

found  in  buttermilk.  C.  0.  Jensen  states  that  the  lactic- 
acid  bacteria  even  succumb  at  about  .75  per  cent  acidity. 
Too  sour  starters  may  therefore  cause  a  great  deal  of 
damage — first  of  all  because  injurious  bacteria  have  been 
allowed  to  multiply  in  them.  When  these  reach  the  cream 
they  are  again  placed  under  unfavorable  conditions,  but  even 
if  they  are  not  allowed  to  multiply  there  to  any  appreciable 
extent  they  will  be  present  in  relatively  large  numbers  and 
go  over  into  the  small  gatherings  of  liquids  in  the  butter. 
The  acidity  will  easily  increase  farther  and  butyric-acid 
bacteria,  if  present,  will  start  their  fermentation— rancid, 
spoilt  butter  being  the  result.  Other  bacteria,  as  those  of 
"  oily  butter,"  may  in  the  same  way  be  propagated  from 
the  starter  to  the  butter.  It  is  therefore  of  the  greatest 
importance  to  keep  the  fermentations  in  the  starter  in 
check.  No  bacteriological  analyses  or  other  intricate 
methods  are  necessary  to  determine  when  the  starter  is 
done  and  when  the  fermentation  should  be  stopped  by 
cooling.  A  skilled  butter-maker  can  easily  determine  the 
question  by  taste,  odor,  and  appearance  of  the  starter.* 

The  proper  ripening  of  the  cream  is,  as  has  often  been 
stated,  one  of  the  most  difficult  problems  of  dairying,  since 
it  can  very  easily  fail  or  be  influenced  by  exterior  condi- 
tions. It  is  above  all  essential  here  as  everywhere  else  to 
observe  the  most  minute  cleanliness,  and  to  watch  all  one's 
movements  to  prevent  any  possible  infection  to  the  cream. 

At  many  places  the  cream  is  run  directly  from  the  sep- 
arator into  the  ripening-vat;  but  this  method  is  to  be  re- 
jected, as  all  kinds  of  irregularities  in  the  ripening  of  the 
cream  will  easily  then  arise  whereby  the  solidity  and  grain 

*  See  foot-note  on  p.  227, 


226  MODERN    DAIRY    PRACTICE. 

of  the  butter  may  suffer.  The  cream  should  be  cooled 
strongly  and  kept  for  a  while  at  a  low  temperature.  Weig- 
mann  gives  observations  in  a  similar  direction,  and  is  of  the 
opinion  that  such  a  cooling  (for  at  least  four  hours)  weak- 
ens the  vital  power  of  the  bacteria  in  the  cream.  It  is  also 
beneficial  to  keep  the  temperature  of  the  cream  uniform 
by  occasional  stirrings,  thus  securing  an  even  ripening  and 
removing  odors,  etc.,  possibly  present  in  the  cream.  It  is 
of  course  greatly  preferable  to  pasteurize  and  then  cool  the 
cream  immediately  after  the  separation. 

The  ripening  of  the  cream  is  usually  finished  within 
18-20  hours  in  our  creameries.  This  is  called  slow  ripen- 
ing /  the  rapid  ripening  lasts  6-10  hours.  The  question 
which  of  the  two  is  preferable  is  at  the  present  one  of 
the  points  of  dissension  in  dairying. 

The  length  of  the  ripening  period  depends  on  (1)  the 
quantity  of  starter  used,  and  (2)  the  temperature  at  which 
the  cream  is  kept.  If  a  high  temperature  and  a  large 
quantity  of  starter  be  used,  the  ripening  will  of  course 
take  place  rapidly.  By  varying  both  factors  the  ripening 
may  take  place  in  the  time  which  experience  has  shown 
the  most  preferable  under  the  conditions  present.  The 
duration  of  the  ripening  period  is  in  my  opinion  not  so 
important  for  a  successful  ripening  of  the  cream  as  are 
the  quality  of  the  cream  and  the  starter,  and  the  degree  of 
cleanliness  which  pervades  the  whole  process.  In  my  first 
pure- culture  experiments  I  used  such  small  quantities  of  the 
starter  that  it  took  thirty-six  hours  to  ripen  the  cream,  and 
a  well-keeping,  fine  butter  was  obtained  ;  on  the  other 
hand,  as  good  and  perhaps  better  may  be  obtained  by  a 
short  ripening  period  when  the  proper  precautions  are 
preserved.  This  being  the  case  nothing  is  gained  by  a  long 


TREATMENT   OF   CKEAM   PREVIOUS   TO   THE   CHURNING.   227 

ripening,  since  the  time  during  which  the  cream  may  be 
infected  with  bacteria  is  thus  only  increased. 

In  rapid  ripening  greater  watchfulness  is  necessary 
and  the  progress  of  the  fermentation  must  be  repeatedly 
examined,  for  the  rapidity  of  the  process  greatly  increases 
the  danger  of  its  progressing  too  far.  It  may  be  added, 
that  if  the  cream  turns  too  acid,  lumps  of  casein  will  sepa- 
rate out  and  later  on  be  taken  up  by  the  butter,  which  will 
then  not  keep  well,  casein,  as  is  well  known,  being  very  un- 
stable and  easily  attacked  by  putrefactive  bacteria.  When 
ripe  for  churning,  the  cream  should  not  contain  any  sepa- 
rated lumps  of  casein. 

The  cream  must  not,  on  the  other  hand,  be  ripened  too 
little,  as  the  taste  will  then  not  be  as  desired;  the  souring 
will  continue  in  the  butter  and  will  there  take  place  under 
wholly  new  conditions,  the  regulation  of  which  we  have 
not  in  our  power.  A  good  acidity,  not  too  mild  and  not 
too  strong,  is  most  desirable  for  the  production  of  a  well- 
keeping  butter.* 

*  It  would  be  of  great  advantage  to  butter-makers,  and  more 
especially  to  novices  among  them,  to  possess  a  method  by  which  the 
proper  acidity  of  the  cream  could  be  accurately  determined.  In 
laboratory- work  and  in  investigations  conducted  by  dairy  chemists 
the  method  of  titration  of  the  cream  by  means  of  an  alkali  has  long 
been  practised,  but  it  was  not  adapted  to  factory  purposes  in  our 
country  until  1890,  when  Dr.  Manns  published  (Bull.  9,  111.  Exp. 
Station)  what  is  known  as  Manns'  Acid  Test.  The  method  rests  on  the 
principle  that  the  compound  phenol phtalein  gives  an  intensely  red 
color  to  alkaline  solutions  ;  a  solution  of  an  alkali  (either  potash,  soda, 
lime,  or  baryta  may  be  used)  of  known  strength  is  added  until  the 
liquid  assumes  a  permanent  red  color,  and  the  acidity  of  the  cream  can 
then  be  calculated.  The  description  of  the  Manns  test  is  given  as 
follows : 

Directions  for  the  Use  of  Manns'  Test:— I.  Stir  the  cream  thor- 


228  MODERN   DAIRY   PRACTICE. 

In  case  the  butter  is  consumed  within  a  short  time  a 
mild  acidity  of  the  cream  may  be  all  right,  but  if  intended 
to  be  kept  for  a  longer  time  (as  in  case  of  export  butter) 
the  ripening  should  be  allowed  to  proceed  farther. 

If  a  good  starter  made  from  a  pure  culture  is  available, 
a  comparatively  large  quantity  may  advantageously  be  used 
to  secure  a  rapid  ripening  of  the  cream.  This  would  seem 
especially  important  in  case  the  cream  is  poor  and  impure, 
for  the  injurious  bacteria  found  in  it  are  then  at  once 
placed  in  minority  ;  a  mass  infection  of  the  cream  is 
started  by  which  means  the  undesirable  forms  of  bacteria 
are  prevented  from  developing. 

Pure  Cultures  and  Shallow  Setting. — It  may  be  of  inter- 
est in  this  connection  to  examine  in  how  far  pure  cultures 

oughly;  insert  small  end  of  pipette  in  cream  and  draw  until  nearly 
full ;  then  put  the  finger  over  upper  end  of  pipette  and  allow  cream 
to  escape  slowly  (by  admitting  air)  until  mark  on  neck  of  pipette  is 
reached.  Transfer  to  a  tumbler  ;  rinse  the  pipette  three  times  with 
lukewarm  water,  adding  the  rinsing  water  to  the  cream  in  the  tumbler. 
Now  add  to  contents  of  the  tumbler  three  drops  of  the  solution 
marked  ' '  Indicator  "  (phenolphtalein). 

2.  Fill  the  burette  up  to  the  O  mark  with  the  solution  marked 
"  Neutralizer  "  (alkali  solution). 

3.  While  constantly  stirring  the  cream  with  the  glass  rod,  allow 
the  liquid  to  flow  from  the  burette  into  the  tumbler  until  the  entire 
contents  of  the  tumbler  shows  a  pink  tinge.     Stop  adding  the  solu- 
tion from  the  burette  the  moment  the  color  is  permanent. 

4.  Read  the  level  of  the  liquid  remaining  in  the  burette.    The 
reading  shows  the  amount  of  acid  present. 

The  experience  of  those  using  the  test  indicates  that  where  the 
acidity  of  the  cream  is  right,  to  secure  the  best  results  in  yield  and 
flavor  of  butter  from  38  to  42  cc.  of  the  neutralizer  will  be  required 
for  the  test.  It  is  a  simple  matter  for  each  butter-maker  to  learn  by 
experiment  the  exact  degree  of  acidity  and  churning  temperature 
suited  to  the  best  results,  and  with  these  as  standards  reduce  the 


TREATMENT  OF   CREAM   PREVIOUS  TO   THE  CHURNING.    229 

are  applicable  in  case  of  the  shallow  setting  system  of 
creaming.  In  experiments  in  this  line  I  prepared  the  acid 
starter  by  means  of  pure  cultures,  in  the  manner  given 
before,  added  the  same  to  the  milk,  and  found  that  in  this 
way  a  much  more  rapid  and  more  certain  fermentation 
was  obtained  than  by  the  ordinary  plan.  The  main  condi- 
tion of  a  successful  outcome  proved  to  lie  in  proper  re- 
striction of  the  fermentation,  so  that  the  casein  of  the 
milk  does  not  coagulate  before  the  creaming  was  done. 
The  butter  made  kept  very  well,  especially  when  the  milk 
was  pasteurized  and  cooled  previously  to  setting. 

Lactic-acid  Bacteria. — A  large  number  of  bacteria  pos- 

process  of  butter-making  to  a  certainty.  By  testing  his  cream  in 
the  afternoon,  the  butter-maker  will  be  able  to  set  it  to  ripen  at  such 
a  temperature  that  it  will  show  the  proper  acidity  for  churning  the 
next  morning. 

In  testing  the  milk  for  cheese-making  the  same  directions  are  to 
be  followed,  excepting  that  a  much  less  acid  condition  is  required  ; 
probably  from  15-20  cc.  will  give  the  best  results.  The  whole  num- 
bers are  cubic  centimeters  ;  the  intermediate  divisions  are  fractions 
of  a  cubic  centimeter. 

Precautions  in  Using  the  Test. — The  solution  marked  "  Neutral  - 
izer"  is  prepared  of  a  certain  strength.  It  is  essential  that  this 
strength  remain  constant.  Never  let  this  solution  stand  without  a 
stopper.  Keep  in  glass  or  stoneware." 

The  necessary  apparatus  and  chemicals  may  be  obtained  from 
dealers  in  dairy  supplies.  Lately  Prof.  Farringtou  has  published  a 
method  of  testing  the  acidity  of  cream  with  alkaline  tablets  of  a  cer- 
tain strength.  For  a  description  of  the  manner  of  procedure  in  ap- 
plying the  tablets,  see  Bull.  No.  32,  111.  Agr.  Experiment  Station. 

Concerning  the  relation  of  the  acidity  of  the  cream  to  the  yield 
of  butter,  see  Sebelien,  Landw.  Versuc7is-Stationen,  34  (1887),  p. 
93 ;  Manns,  Bull.  9,  111.  Agr.  Experiment  Station  (1890) ;  Wallace, 
Bull.  No.  22,  Iowa  Agr.  Experiment  Station  (1894). 


230  MODERN    DAIRY    PRACTICE. 

sess  the  quality  of  producing  lactic  acid  iu  the  milk  ;  they 
are  able  to  develop  at  temperatures  above  52°  F.  (11°  C.) 
—the  optimum  temperature  as  regards  their  power  of  fer- 
mentation lying  between  82°  and  100°  F.  (28°  and  38°  C.). 
The  different  bacteria  show  great  differences,  however,  as 
regards  both  their  optimum  temperature  and  the  different 
substances  besides  lactic  acid  which  they  produce  in  milk. 
The  majority  of  the  lactic-acid  bacteria  are  aerobic ;  the 
statements  made  in  some  text-books  to  the  effect  that  these 
organisms  cannot  give  rise  to  regular  fermentations  in  the 
presence  of  air  are  therefore  erroneous.  The  advantage  of 
stirring  the  cream  during  the  ripening  is  apparent  from  this. 

If  the  sour  milk  or  cream  found  in  practice  is  exam- 
ined bacteriologically,  we  usually  find  that  several  differ- 
ent kinds  of  lactic-acid  organisms  are  active  in  it  at  the 
same  time,  and  that  neighboring  creameries  may  operate 
with  wholly  different  forms  of  lactic-acid  bacteria.  Storch 
also  says  in  his  comprehensive  and  valuable  work  on  the 
"  Souring  of  the  Cream " :  "  Every  time  I  obtained  new 
samples  of  butter  I  received  new  bacteria.  The  explana- 
tion that  there  are  no  two  lots  of  butter  in  Denmark  pos- 
sessing exactly  the  same  flavor  is  found  in  this." 

This  is  not  the  place  to  treat  exhaustively  the  special 
qualities  and  morphological  characteristics  of  the  different 
lactic-acid  bacteria.*  Some  few  observations  on  this  point 
may  properly  be  made  here,  however.  All  investigations 

*  Those  studying  these  questions  are  referred  to  the  work  by  V. 
Storch,  just  mentioned,  to  the  special  reports  by  H.  Weigmann  in 
Laiidw.  WocJienbl.  f.  Schleswig-Holstein,  to  G.  Marpmann's  article  in 
Erganzungsliefte  zum  Centralbl.  f.  allgemeine  Gesundheitspflege,  1886, 
to  C.  O.  Jensen's  bacteriological  investigations  reported  in  Bull.  22 
of  Copenhagen  Arg.  Exp.  Station,  to  L.  Adametz's  researches,  a 
summary  of  which  was  given  at  the  Agricultural  Congress  in  Vienna, 


TREATMENT   OF   CREAM   PREVIOUS   TO   THE   CHURNING.    231 

have  thus  shown  that  cream  can  be  ripened  by  means 
of  carefully-prepared  pure  cultures  in  such  a  manner  that 
pure  and  well-keeping  butter  is  made  from  it,  but  that 
there  seem  special  difficulties  in  obtaining  a  distinct  flavor 
in  the  butter.  Bacteriologists  have  gone  to  a  great  deal  of 
trouble  in  searching  for  a  bacteria  which  would  produce 
not  only  a  strong  fresh  acid  taste,  but  a  good  flavor,  with 
but  little  success;  so  that  Spallanzani  finally  says  in  de- 
spair that  fine  flavor  and  keeping  quality  are  character- 
istics which  only  to  a  certain  extent  go  hand  in  hand,  and 
Weigmann  doubts  that  there  is  any  single  bacterium  possess- 
ing the  faculty  of  bringing  about  this  double  end.  Jensen 
makes  the  following  demands  to  a  lactic-acid  bacterium  to 
be  used  in  creameries :  (1)  that  it  will  sour  the  cream  rather 
strongly  in  comparatively  short  time,  so  that  it  can  com- 
pete with  other  bacteria  present;  (2)  that  it  will  thrive  at 
a  relatively  low  temperature  (60°-72°  F.);  (3)  that  it  will 
coagulate  the  cream  and  milk  to  a  uniform  homogeneous 
mixture,  and  give  it  a  slightly  sour  taste  and  odor;  (4)  that 
it  will  produce  an  agreeable  aromatic  taste  and  flavor. 
But,  he  adds,  we  know  at  the  present  no  acid  bacterium 
that  fills  all  these  conditions. 

In  my  experiments  along  this  line  I  have  not,  among 
the  numerous  bacteria  examined,  been  able  to  show  any  one 
bacterium  possessing  all  the  valuable  qualities  desired;  but 
by  cultivating  two  different  organisms,  and  mixing  them 
at  the  same  time  in  the  milk  used  for  a  starter,  I  have  suc- 
ceeded in  obtaining  a  starter  which  produced  both  good 
acid  and  an  excellent  flavor  in  the  cream.  I  have  either 

1890,  to  "  Die  Milch  "  by  H.  Scholl,  1891,  and  to  nay  book  on  "  Sap- 
rophytic  Micro-organisms  in  Cow's  Milk  "  (in  Swedish),  published 
1889.— G.G. 


232  MODERK    DAIRY   PRACTICE 

used  a  short  bacterium  previously  described  by  me  *  under 
the  name  of  'bacterium  acidi  lactici  as  acid-former,  or  an- 
other longer  staff -like  bacterium  which  I  have  found  present 
in  many  places  in  our  country.  Both  these  organisms 
produce  a  very  marked  and  pleasant  acidity,  develop  well 
under  ordinary  creamery  conditions,  and  seem  splendidly 
adapted  to  this  object.  Neither  produce  any  special  flavor 
in  the  cream  or  the  butter,  but  do  not,  on  the  other  hand, 
give  undesirable  qualities  to  it.  I  have  obtained  flavor  by 
the  application  of  either  of  these  bacteria  in  connection 
with  one  of  the  yeast-fungi  previously  described  f  as  pro- 
ducing both  alcohol  and  lactic  acid  in  milk.  This  yeast- 
fungus,  which  I  have  found  in  sour  and  in  stringy  milk  in 
several  parts  of  our  country,  thrives  very  well  together 
with  either  of  the  before-mentioned  lactic-acid  bacteria. 
By  the  co-operation  of  these  organisms  the  cream  obtained 
an  agreeable  acid  and  flavor,  and  the  butter  seemed  to 
keep  well  and  was  of  good  taste  and  flavor.  By  cultivat- 
ing several  distinct  bacteria  in  symbiosis  in  this  way  it 
seems  that  very  favorable  results  may  be  obtained,  if  I  in- 
terpret rightly  the  data  now  at  hand.  J 

*  Fortschritte  der  Medicin,  vol.  vii.  pp.  124-131. 

f  Loc.  cit.,  and  p.  107  of  this  work. 

t  Literature  on  the  subject  of  pure  cultures  :  Storch,  "  Flodens 
Syrning"  (Ripening  of  the  Cream),  18th  Report  Copenhagen  Experi- 
ment Station,  1890  ;  Biedermann's  Centralblatt,  20,  p.  48  ;  Weigmann, 
"Use  of  a  Pure  Lactic  Germ  for  Ripening  Cream/'  Milchzeitung, 
1890  and  1892  ;  Ldw.  TJiierzutfit,  1891,  527  ;  Hyg.  Rundschau,  1892, 
No.  17  ;  Adametz  and  Wilckens,  "  Souring  of  Cream  by  Pure  Cult- 
ures of  Bacteria,"  Ldw.  Jahrb.,  21,  p.  131  ;  Lafar,  "  Artificial  Sour- 
ing of  Cream  by  Pure  Culture,"  Oest.  Ldw.  WochenbL,  1893,  Nos.  16 
and  19  ;  Klein  and  Kiihn,  "Experiments  with  Pure  Cultures,"  Der 
Landwirt  1893,  No.  53  ;  Biederm.  Cenlralbl.  1894,  p.  459  ;  Conn, 
"  The  Fermentations  of  Milk,"  1892,  pp.  67-69  ;  Georgeson,  "  Dairy 
Industry  in  Denmark,"  1893,  pp.  44-46.— W. 


TREATMENT  OF  CREAM   PREVIOUS  TO  THE   CHURNING.    233 

Latest  Investigations.* — Since  the  above  was  written 
(1891)  the  question  of  the  application  of  pure  cultures  in 
the  ripening  of  the  cream  has  taken  a  great  step  forward 
so  that  it  now  may  be  safely  said  that  the  problem  is  prac- 
tically solved.  Pure  cultures  that  will  keep  are  now  in  the 
market;  they  are  put  up  in  a  practical  manner,  and  as  a 
rule  contain  pure  distinct  cultures  of  bacteria.  Denmark 
has  again  taken  the  lead  in  this  matter,  and  now  furnishes 
an  article  which  is  as  easily  applied  as,  e.g.,  rennet  extract. 
According  to  what  I  have  been  able  to  ascertain  pure  cult- 
ures can  be  bought  in  Denmark  from  not  less  than  three 
firms — Blauenfeldt  and  Tvede,  Copenhagen ;  Chr.  Hansen, 
Copenhagen;  and  Quist  of  Nonneberg. 

Pure  cultures  inoculated  in  a  fluid  were  at  first  intro- 
duced in  the  trade,  but  it  was  impractical  both  to  ship 
and  to  apply  the  cultures  as  put  up  in  vials.  Such 
liquid  pure  cultures  do  not,  on  the  whole,  seem  to  be  able 
to  keep  very  well;  they  may,  however,  be  applied  with  ad- 
vantage if  they  can  be  used  when  fresh  and  are  kept  under 
favorable  conditions;  the  shape  of  the  vials  in  which  the 
cultures  are  shipped  has  also  been  improved  of  late.  The 
solid  pure  cultures  recently  placed  on  the  market  are  bet- 
ter, especially  if  the  pure  culture  cannot  be  secured  fresh. 
These  can  stand  being  kept  for  months,  even  half  a  year, 
without  being  appreciably  changed  in  their  qualities. 

At  the  creamery  of  the  Mustiala  Dairy  Institute,  solid 
normal  starter  from  Danish  Butter  Color  Company,  Blau- 
enfeldt and  Tvede,  Copenhagen,  is  at  the  present  being 
used  with  great  success.  In  applying  it  the  following  di- 
rections given  by  the  manufacturers  are  followed : 

*  Author's  addition  to  the  present  translation. 


234  MODERN    DAIRY    PRACTICE. 

1.  "  Treatment  of  the  Solid  Starter  as  it  Comes  from 
the  Laboratory. — Ten  liters  of  skimmed  milk  are  heated  to 
176°  F.  (80°  C.),  kept  for  two  hours  at  that  temperature, 
and  then  cooled  to  90°  F.  (32°  C.).     The  whole  contents 
of  the  vial  are  then  added  and  carefully  mixed  with  the 
milk.     The  milk  is  placed  in  warm  water,  which  must  be 
kept  at  the  same  temperature  throughout  the  souring,  and 
the  can  is  covered  lightly — e.g.,  with  cheese-cloth.   The  milk 
sours  evenly  after  about  eighteen  hours,  when  it  is  cooled 
and  left  undisturbed  until  it  is  to  be  used.     The  upper 
layer  is  skimmed  off  before  using  the  milk.     The  starter 
has  a  pure  acid  taste;  it  is  somewhat  granular,  but  this 
will  entirely  disappear  during  the  later  treatment. 

2.  Treatment  of  the  Starter  from  Day  to  Day. — In  the 
later  treatment  a  quantity  of  skim-milk  is  taken  sufficient 
both  for  the  souring  of  cream  and  for  next  day's  milk. 
The  milk  is  heated  to  176°  F.  (80°  C.)  for  two  hours,  then 
cooled  to  82°  F.  (28°  C.),  and  a  quantity  of  the  starter  pre- 
pared the  preceding  day  is  added,  corresponding  to  ten  per 
cent  of  the  milk  (one  liter  per  ten  liters).     The  starter 
should  be  ready  in  six  to  seven  hours.     It  must  be  carefully 
watched,  so  that  the  temperature  does  not  sink  below  81°  F. 
(27°  Q.)  during  the  ripening.     When  the  starter  is  done 
it  is  at  once  placed  in  ice-water,  where  it  is  left  without 
stirring  until  it  is  to  be  used.     The  following  days  we  pro- 
ceed in  the  same  manner;  a  sufficient  quantity  of  skim- 
milk  is  pasteurized,  ten  per  cent  of  the  preceding  days' 
starter  is  added;  and  so  on  until  a  new  pure  culture  is 
taken. 

The  ripening  of  the  cream,  churning,  and  all  the  other 
work  in  the  creamery  are  conducted  in  the  ordinary  man- 
ner. The  temperatures  are  kept  as  usual.  In  the  ripen- 


TREATMENT  OF  CREAM  PREVIOUS  TO  THE  CHtJRNlHG.    235 

ing  of  the  cream  it  must  be  observed  that  this  does  not 
turn  too  sour;  this  is  easily  avoided,  however,  if  the  cream 
is  cooled  just  when  the  right  degree  of  ripeness  is  obtained, 
or  if  the  cream  is  kept  somewhat  cooler  the  next  time. 

New  acid  starter  ought  to  be  prepared  every  day  instead 
of  using  buttermilk,  as  in  this  manner  bacteria  are  best 
prevented  from  being  introduced  by  bad  milk.  How  often 
the  normal  acid  starter  is  to  be  renewed  depends  on  so 
many  conditions — as  the  care  used  in  preparing  the  starter 
and  in  preserving  it,  the  quality  of  the  milk,  etc.,  that  it  is 
difficult  to  give  any  rule;  but  it  may  be  done  from  once  a 
month  to  once  a  week.  If  it  should  happen  that  the 
starter  is  not  good  or  will  not  keep,  it  either  comes  from  lack 
of  care  in  the  preparation,  or  from  the  fact  that  the  milk 
used  is  not  germ-free,  the  heating  done  having  not  been 
sufficient  to  kill  the  bacteria.  Private  dairies  are  in  such 
cases  advised  to  take  the  milk  from  three  cows  and  skim  it 
next  day,  and  then  treat  it  as  mentioned  above.  At 
creameries  good  morning  milk  from  a  single  patron  is 
taken  for  a  starter.  If  it  should  happen  that  starter  is 
not  ready  when  needed,  owing  to  milk  being  too  cold,  the 
starter  is,  without  being  stirred,  placed  in  a  vessel  with 
water  at  77°-81°  F.  (25°-27°  C.),  according  to  the  season, 
when  it  will  be  ready  in  from  one  to  two  hours.  In  this 
heating  process  it  must  be  carefully  watched,  that  the 
starter  is  rapidly  cooled  as  soon  as  done. 

The  best  results,  in  using  normal  acid  starter  for  ripen- 
ing will  be  obtained  when  the  cream  is  pasteurized. 

One  lot  of  normal  acid  starter  is  sufficient  for  about 
ten  kilos  (22  Ibs.  or  a  little  more  than  2i}  gals.)  of  skim- 
milk.  The  following  proportions  of  cream  and  starter 
should  be  observed: 


236  MODERN   DAIRY    PRACTICE. 

For  pasteurized  cream,  5-10  per  cent. 

For  non-pasteurized  cream  at  proprietary  creameries,  4 
per  cent  or  more. 

For  non-pasteurized  cream  at  other  creameries,  5  per 
cent  or  more.  All  vessels  and  utensils  must  be  kept  care- 
fully clean.  '  Normal  acid  starter '  is  kept  stoppered,  and 
the  whole  quantity  used  at  once." 

This  carefully-prepared  method  should  be  strictly  fol- 
lowed, even  in  minute  details,  if  the  full  benefit  is  to  be 
derived  from  it.  I  must  particularly  warn  inexperienced 
persons  against  "  improving  the  same  "  or  "  making  it  sim- 
pler/' Only  uncertainty  is  gained  thereby,  and  the  real 
benefit  is  lost. 

It  must  finally  be  emphasized,  in  speaking  of  pure  cult- 
ures as  fermentation  starters  for  ripening  of  cream,  that 
in  the  majority  of  cases  it  will  hardly  pay  the  trouble  of 
applying  such  if  the  cream  to  he  ripened  be  not  previously 
pasteurized.  The  cream  may  contain  so  large  a  number 
of  injurious  bacteria  that  the  favorable  influence  of  the  pure 
culture  is  greatly  diminished  and  may  even  be  abolished. 
Pasteurization  of  the  cream  may  be  compared  with  a  fallow 
field,  in  which  nearly  all  weeds  are  killed,  and  a  good  acid 
starter  with  ^ure  and  good  seed.  It  is  of  but  little  use  if 
such  seed  is  sown  in  a  soil  full  of  weed-seeds  capable  of 
germination;  in  the  same  way  it  is  of  but  little  benefit  to 
add  a  pure  culture  to  a  cream  containing  many  injurious 
bacteria.  The  impurities  may  overpower  the  good  seed, 
and  the  result  will  be  poor. 


CHAPTER  II. 
THE  MANUFACTURE  AND  HANDLING  OF  BUTTER. 

THE  cream  having  been  properly  ripened,  the  churn- 
ing may  take  place.  Also  during  this  process  it  is  neces- 
sary to  observe  all  kinds  of  precautions  to  protect  the 
cream  from  infection.  The  churn  should  as  far  as  possible 
be  sterile  and  should  be  aired  and  steamed  before  being 
used.  A  very  common  mistake  in  creameries  is  to  leave 
the  churn  standing  without  cover  in  an  upright  position 
when  not  in  use,  as  it  were,  to  catch  all  the  dust  and  the 
bacteria  slowly  settling  from  the  air.  Some  water  will 
usually  gather  at  the  bottom  of  the  churn;  and  with  high 
temperatures  as  a  rule  reigning  in  our  creameries,  we  have 
conditions  very  favorable  to  bacterial  growth,  and  that  in 
the  very  vessel  in  which  the  butter  is  to  be  manufactured. 
It  will  not  improve  the  matter  if  the  cover  is  always  kept 
on  the  churn,  as  this  will  then  not  properly  dry  out.  The 
churn  should  be  kept  upside  down  when  not  in  use,  or  if 
movable  should  be  kept  out  of  the  way.  The  temperature 
of  the  churn  should  be  properly  adjusted  before  the  churn- 
ing by  rinsing  it  with  recently-melted  iced  water  or  boiled 
and  subsequently  cooled  water.  If  the  churn  is  kept  in  a 
proper  manner,  no  special  sterilization  will  be  necessary 
directly  before  the  churning. 

In  order  to  get  through  early  with  the  creamery-work, 
the  cream  is  in  many  places  churned  and  even  the  butter 

337 


238  MODERN    DAIRY    PRACTICE. 

worked  early  in  the  morning  before  it  is  perfectly  light. 
This  custom  ought  not  to  be  followed,  for  it  is  impossible 
to  observe  the  necessary  cleanliness  in  semi-darkness,  and 
to  make  the  necessary  and  accurate  observations  without 
which  a  good  churning  and  working  cannot  be  accom- 
plished. The  work  should  take  place  in  full  daylight  from 
beginning  to  end;  if  the  creamery-work  thereby  extend 
somewhat  later  it  cannot  be  helped. 

The  butter  can  lose  its  keeping  quality  already  in  the 
churn — above  all  by  the  application  of  a  wrong  churning 
temperature,  so  that  it  cannot  be  properly  freed  from  the 
buttermilk.  The  butter  granules  should  remain  separate 
and  clear  at  the  end  of  the  churning,  and  the  buttermilk 
easily  drain  from  the  butter. 

When  the  butter  has  come  all  operations  aim  at  the 
complete  removal  of  the  buttermilk  particles  from  the 
butter.  As  shown  by  Duclaux,  pure  butter  fat  is  not  a 
nutritive  medium  for  the  bacteria;  but  besides  fat,  butter 
contains  both  air  and  water,  as  well  as  buttermilk,  with  its 
ash  materials  and  albuminoid  substance.  It  is  from  the 
albuminoids  (casein,  albumen,  etc.)  that  danger  of  spoiling 
threatens,  for  they  are  especially  readily  attacked  by  bac- 
teria and  furnish  them  with  the  necessary  nutrients.  The 
importance  of  diminishing  the  quantity  of  buttermilk 
present  in  the  butter  is  therefore  evident;  it  would  doubt- 
less increase  the  keeping  quality  of  the  butter  if  the  butter- 
milk could  be  entirely  removed,  but  the  butter  would  then 
lose  its  peculiar  flavor  and  become  fat  pure  and  simple. 

The  importance  of  a  small  bacteria  content  of  the 
buttermilk  also  follows  from  what  has  been  said.  It  is 
intimately  mixed  with  the  butter,  and  forms  a  favorable 
breeding-place  for  the  fermentation  bacteria  dangerous  to 


THE   MANUFACTURE   AND   HANDLING   OF   BUTTER.    239 

the  keeping  quality  and  flavor  of  the  butter.  The  buttermilk 
is  nothing  but  the  cream  minus  the  butter,  and  the  maker 
who  secures  cream  of  a  good  quality  at  the  same  time 
gains  good  means  of  transferring  this  quality  to  the  butter. 

Influence  of  Air  and  Light. — But  the  keeping  quality 
of  the  butter  also  depends  on  other  conditions  than  the 
quality  and  the  amount  of  buttermilk  in  it.  Duclaux  has 
shown  through  numerous  experiments  that  the  butter 
must  be  protected  from  the  influence  of  air  (oxygen)  and 
light.  Precautions  in  this  direction  should,  he  says,  be 
taken  even  in  the  churn — e.g.,  by  washing  the  butter  with 
water  poor  in  oxygen ;  well-water  or  spring  water  should 
be  used  for  washing  and  not  lake  or  rain  water.  Duclaux 
considers  the  latter  injurious  both  on  account  of  their 
larger  content  of  oxygen,  as  well  as  the  probable  presence 
of  numerous  micro-organisms  in  them.  The  advantage 
of  the  application  of  ice-water  for  this  purpose  has  already 
been  dwelt  on  (see  p.  136).  The  butter  must  farther  be 
protected  from  direct  sunlight. 

Some  dairymen  advocate  washing  the  butter  with  skim- 
milk;  but  this  practice  cannot  be  recommended,  as  the 
casein  of  the  skim-milk  will  be  coagulated  by  the  acid 
buttermilk,  and  cannot  be  completely  removed  by  subse- 
quent washing  and  working  of  the  butter.  The  butter 
may  advantageously  be  washed  with  ice-water  (about  4°  C.), 
as  is  done  in  the  making  of  "Paris  butter."  The  cold 
water  will  harden  the  butter  granules  and  favor  the  ex- 
pulsion of  the  buttermilk;  the  butter  as  a  result  will  con- 
tain less  water  and  less  buttermilk.  Warmer  wash-water 
does  not  seem  to  produce  the  same  effect.  It  is  objected 
that  the  butter  is  apt  to  be  too  hard  by  this  method,  but 
this  shortcoming  can  *be  remedied  in  the  workim 


240  MODERN   DAIRY   PRACTICE. 

Whether  this  strong  cooling  is  applicable  under  all  condi- 
tions in  the  manufacture  of  sour-cream  butter  I  cannot 
say;  the  method  has  proved  very  satisfactory  in  the  manu- 
facture of  "  Paris  butter." 

The  churning  should  not  be  stopped  too  soon ;  the  but- 
ter granules  ought  to  be  well  formed  before  being  taken 
out  of  the  churn  (about  the  size  of  wheat-kernels  or 
smaller).  In  taking  the  butter  out  of  the  churn  it  is  often 
rinsed  with  water;  this  method  is  hardly  to  be  recom- 
mended. It  arises  from  the  desire  to  obtain  a  mildly-acid 
butter  or  one  entirely  free  from  acidity,  resembling  some- 
what sweet-cream  butter  in  taste.  It  frees  the  butter  from 
excessive  acid  and  buttermilk,  but  the  flavor  of  the  butter 
will  be  apt  to  suffer  at  the  same  time.  The  ripening  may 
therefore  rather  be  conducted  so  that  no  excessive  acidity 
arises  and  the  churning  so  arranged  that  the  buttermilk 
drains  off  without  such  a  washing. 

When  the  butter  is  taken  out  of  the  churn  it  is  usually 
left  in  the  butter-trough  for  a  while  to  allow  the  buttermilk 
to  drain  off.  The  butter  should  here  be  kept  covered  to 
prevent  dust,  etc.,  from  falling  into  it,  and  so  as  not  to 
expose  it  to  the  action  of  light. 

Working  the  Butter. — The  butter  worker  should  re- 
peatedly be  washed  with  boiling-hot  water  before  being  used 
and  then  cooled  with  iced  water.  It  is  at  present  the 
fashion  at  our  creameries  to  work  the  butter  very  lightly  the 
first  time,  so  that  a  good  deal  of  buttermilk  is  left  in  it.  By 
this  method,  which  springs  from  a  fear  of  overworking  the 
butter,  it  seems  to  me,  however,  that  the  matter  is  brought 
over  on  the  wrong  track,  for  the  only  chance  for  a  com- 
plete separation  of  unnecessary  buttermilk  from  the  butter 
is  offered  in  the  first  working.  In  my  opinion  all  pos- 


THE   MANUFACTURE   AND    HANDLING    OF    BUTTER.    241 

sible  pains  should  be  taken  to  make  the  working  thor- 
ough. But  the  overworking  ? — it  is  objected.  "  If  the 
butter  is  overworked  it  will  not  give  off  its  buttermilk  and 
cannot  possibly  keep  well."  This  is  correct,  but  it  is  also  a 
fact  that  if  the  churning  has  been  properly  done  the  first 
working  can  very  well  be  made  so  thorough  that  the 
greater  portion  of  the  buttermilk  may  be  removed  without 
risking  any  overworking  of  the  butter.  It  seems  to  me 
that  it  is  a  confession  of  lack  of  ability  on  the  part  of  the 
butter-maker  to  say  that  his  butter  cannot  be  properly 
worked  the  first  time  without  being  overworked;  Only 
sufficient  buttermilk  should  remain  in  the  butter  at  the 
first  working  as  is  necessary  for  the  solution  of  the  salt. 

Between  the  workings  the  butter  is  kept  cooling  either 
in  tin  trays  or  placed  in  a  cooling-chest,  at  the  bottom  and 
cover  of  which  ice  is  kept.  In  many  creameries  I  have 
seen  colossal  refrigerators  used  for  this  purpose  which  it  is 
very  difficult  to  air  out  properly.  We  therefore  find  in  them 
a  disagreeable,  sour  smell,  and  their  walls  are  often  covered 
with  a  slimy  film  of  bacteria  or  all  kinds  of  molds.  These 
infectious  spots,  with  which  the  butter  comes  in  contact, 
must  of  course  be  removed.  We  also  find  working-troughs 
in  some  creameries  that  are  of  the  same  kind  as  the  cool- 
ing-chests— too  heavy  to  be  carried  outside  and  apt  to  be 
left  to  mold  in  the  moist  creamery.  In  many  respects 
practical  refrigerators  introduced  at  Danish  creameries  are, 
in  my  opinion,  objectionable  for  the  same  reason. 

Salting  the  Butter.— The  butter  should  not  be  salted 
too  early — i.e.,  while  it  still  contains  a  great  deal  of  butter- 
milk. If  this  is  done  the  effect  of  the  salt  to  drive  out 
superfluous  buttermilk  is  largely  lost,  the  fluid  being  in 
this  case  too  much  diluted.  Salt  is  not  added  to  make  up 


242  MODERN   DAIRY   PRACTICE. 

for  the  weight  lost  in  the  working,  but  to  continue  the 
work  which  this  process  could  not  finish.  The  salting  can, 
of  course,  also  be  done  too  late — when  the  butter  is  too  dry 
or  has  already  been  overworked.  The  salt  may  increase  the 
keeping  quality  of  the  butter  to  some  extent.* 

*  Some  writers  argue  that  the  keeping  quality  of  the  butter  is  due 
entirely  to  the  salt  which  it  contains.  This  assertion  is  not  justified, 
however.  While  it  is  well  known  that  salt  has  strong  preserving 
properties  it  does  not  generally  check  the  growth  of  the  pathogenic 
(disease-producing)  bacteria.  The  only  one  of  these  organisms  which 
according  to  Foster's  experiments  was  influenced  by  the  salt  was  the 
cholera  bacillus.  The  typhus  bacterium  was  not  at  all  incommoded 
by  common  salt,  and  tubercle  bacilli  only  after  having  been  exposed 
to  the  action  of  salt  for  a  long  time.  As  regards  the  non-pathogenic 
bacteria  found  in  milk  I  have  ascertained  that  they  are  generally  but 
slightly  influenced  by  salt  that  may  be  present  in  the  substratum. 
If  the  conditions  are  otherwise  favorable  for  these  organisms  even  a 
high  salt  content  in  the  nutritive  solution  will  not  check  their  devel- 
opment. In  the  experiments  mentioned  I  grew  lactic-acid  bacteria, 
among  other  mediums,  in  sterilized  brine  which  had  previously  been 
a  preserving  fluid  for  butter.  They  developed  vigorously  in  it  and 
fully  retained  their  ability  to  produce  lactic  fermentation,  although 
they  went  through  a  long  series  of  inoculations  from  one  sample 
tube  with  sterilized  brine  to  another.  If,  on  the  other  hand,  salt 
was  added  to  this  brine  so  that  the  solution  became  saturated,  the 
lactic-acid  bacteria  developed  only  slowly  and  feebly  and  after  hav- 
ing been  grown  in  3  to  4  such  solutions,  they  died  out  entirely.  As 
regards  the  influence  of  salt  on  other  bacteria  found  in  milk,  I  have 
only  ascertained  that  certain  putrefactive  bacteria  are  very  sensitive 
to  the  action  of  salt,  while  e.g.,  the  butyric-acid  bacillus,  i.e.,  the  form 
of  the  same  with  which  I  have  experimented,  is  only  slightly  dis- 
turbed by  a  high  salt  content  in  the  substratum.  Salt  therefore  in- 
fluences as  a  rule  only  slightly  the  growth  of  bacteria.  It  may  be 
noted  in  this  connection  that  the  preserving  influence  of  salt,  e.g.  in 
butter-making,  is  largely  due  to  the  fact  that  it  indirectly  counteracts 


THE   MANUFACTURE   AND   HANDLING   OF   BUTTER.    243 

Cleaning  of  Churn. — The  buttermilk  should  be  removed 
from  the  churn  as  soon  as  possible  after  the  butter  is  taken 
up,  and  the  cleaning  of  the  latter  should  take  place  at  once. 
The  churn  with  cover  is  washed  with  cold  water  and  then 
brushed  with  hot  water,  after  which  it  is  thoroughly 
steamed,  or  filled  one  fourth  full  with  boiling-hot  water, 
which  is  churned  for  five  minutes  and  then  drained  off. 
The  churn  and  cover  is  carefully  brushed  with  pure  dry 
salt,  and  rinsed  with  hot  water  and  aired.  This  lengthy 
process  has  proved  most  satisfactory  in  practical  creamery- 
work.  When  cleaned  in  this  way  the  churn  will  retain  a 
sweet  smell — which,  I  am  sorry  to  say,  is  not  often  met 
with  in  the  churns  of  our  creameries. 

The  butter  should  be  left  for  some  time  after  salting  to 
allow  the  salt  to  dissolve.  At  a  temperature  of  46°-50°  F. 
the  butter  needs  3-4  hours  before  the  salt  is  dissolved  and 
before  the  consistency  necessary  for  the  last  working  is 
reached. 

When  ready  the  butter  should  be  firm,  of  a  clear,  not 
milky  color;  should  show  a  dry  surface,  and  when  packed 
in  the  tub  should  not  lose  appreciable  quantities  of  brine 
even  during  a  long  transportation. 

The  tub  must  be  properly  cleaned  and  sterilized  before 
the  butter  is  packed  into  it. 

The  butter  is  to  be  packed  closely  and  firmly  in  the  tub 

the  development  of  bacteria.  It  leads  to  unite  the  small  drops  of 
buttermilk  in  the  butter  to  larger,  which  may  be  easily  expelled  ia 
working.  Unfavorable  conditions  are  thereby  created  for  the  bacteria, 
the  moisture  necessary  for  their  development  being  removed  for  the 
larger  portion  of  the  butter  ;  and  the  salt  content  where  some  fluid 
remains  becoming  so  concentrated  that  the  bacteria  are  checked  in 
their  development, 


244  MODERN    DAIRY   PRACTICE. 

so  that  no  air-spaces  will  appear  in  it.  The  rancidity 
seems  to  start  from  such  interstices,  the  butter  being  also 
often  discolored  in  such  places.  The  tub  should  always  be 
packed  full  of  butter;  rather  than  sending  half -filled  tubs 
they  should  be  left  until  next  shipment.  Neither  should 
tubs  be  sent  containing  soft  butter  that  has  not  yet  been 
cooled  for  a  sufficiently  long  time.  Such  butter  cannot 
stand  transportation,  turns  easily  off  flavor,  and  suffers  great 
shrinkage.  There  is  no  harm  done  if  these  tubs  are  left 
till  next  shipment,  if  the  butter  is  well  made  and  tubs 
treated  according  to  directions  given. 

At  most  of  our  creameries  ihe  butter  when  once  in  the 
tubs  is  not  considered  in  need  of  any  farther  care  on  part 
of  the  butter-maker,  and  it  is  largely  left  to  its  own  fate. 
The  tubs  are  Itept  in  an  out-of-the-way  place,  exposed  to 
all  kinds  of  moisture  and  temperatures.  But  much  is  left 
at  stake  in  this  way.  As  before,  bacteria  must  be  prevented 
from  injuring  the  butter,  and  this  can  most  easily  be  done 
by  means  of  cooling. 

Bacteria  in  Butter. — When  packed  a  larger  or  smaller 
number  of  bacteria  is  always  found  in  the  butter.  The 
number  will  differ  according  to  the  treatment  which  the 
milk  received  and  according  to  the  kind  of  butter  produced. 
In  a  sample  of  sweet  cream  butter  examined  baeteriologi- 
cally  I.  found  a  comparatively  small  number  of  bacteria  an 
hour  after  it  was  worked,  and  the  different  samples  of 
"  Paris  butter  "  (see  p.  205)  analyzed  contained  still  fewer 
such  organisms — viz.,  from  120  to  300  per  c.c.  As  would 
be  expected,  a  far  larger  number  have  been  found  in  fresh 
sour-cream  butter — viz.,  not  less  than  2000-55000  per  cc. 
During  the  first  days  a  perceptible  increase  in  the  number 
of  bacteria  was  noticed  in  all  samples  of  butter,  especially 


THE   MANUFACTURE  AND   HANDLING   OF   BUTTER.    245 

in  the  outer  layer.  In  the  centre  of  the  tub  a  compara- 
tively small  increase  took  place  during  the  first  hours,  but  it 
soon  stopped,  at  least  if  the  butter  had  been  well  worked. 
The  lively  bacterial  increase  in  the  surface  layer  spread 
very  slowly  toward  the  centre. 

Lafar  (Munich)  found  an  immense  number  of  bacteria 
in  sour-cream  butter  examined  by  him,  which  presumably 
had  not  received  the  best  treatment.  In  most  samples  ten 
to  twenty  million  bacteria  per  gram  (£%  of  an  ounce)  were 
found,  and  he  adds  that  it  is  not  stretching  matters  to 
assert  that  more  living  organisms  are  often  consumed  with 
an  ordinary  good-sized  sandwich  than  there  are  inhabitants 
in  Europe.* 

The  outer  layers  of  fresh  sour-cream  butter  will  be 
found  to  contain  a  large  number  of  the  bacteria  that  took 
part  in  the  ripening.  But  these  do  not  generally  appear 
to  thrive  long  in  butter,  unless  it  is  soft  and  contains 
a  good  deal  of  buttermilk.  Samples  of  butter  of  different 
origin  have  shown  great  difference  in  this  respect.  If  a 
sample  is  dry  and  hard,  the  lactic-acid  bacteria  and  even 
some  putrefactive  bacteria  will  soon  disappear,  so  that  but- 
ter after  four  or  five  days  will  present  an  entirely  different 
picture  to  the  bacteriologist  than  before.  In  place  of  the 
staff-like  bacilli  found,  other  wholly  different  forms  seem 
to  appear,  such  as  several  kinds  of  sarcina  and  small 
micrococci.  These  forms  multiply  rapidly,  and  according 
to  what  I  have  been  able  to  find  out,  do  not  in  general 
exert  any  bad  influence  on  the  quality  of  the  butter — at 

*  Sigismund  (Inaug.  Dissert.  Univ.  Halle  a.  S.,  1893)  found  from 
26,000  to  over  2,000,000  bacteria  per  gram  in  eight  samples  of 
Halle  butter.— W. 


246  MODERN    DAIRY    PRACTICE. 

least  when  alone.  The  staff-bacteria  have  not  disappeared 
entirely,  but  are  in  a  great  minority. 

If,  on  the  other  hand,  a  sample  of  butter  is  soft  and  con- 
tains large  quantities  of  buttermilk,  the  bacilli  will  retain 
their  superiority  all  the  time;  the  lactic-acid  bacteria  ap- 
pearing first  and  later  on  others,  giving  rise  to  more  or  less 
harmful  fermentations.  The  importance  of  these  condi- 
tions for  the  keeping  quality  of  the  butter  is  evident  without 
any  farther  elucidation. 

If  the  butter  be  cooled,  the  increase  of  bacteria  spoken 
of  will  be  found  to  cease  very  soon.  The  cooling  of  the 
butter  in  tubs  takes  place  very  slowly,  even  if  good  refrig- 
eration is  used,  and  it  seems  especially  to  last  long  before 
the  cooling  reaches  the  centre.  My  investigations  show, 
however,  that  it  is  not  very  important  that  the  cooling  act 
on  this  part  of  the  butter,  as  no  significant  bacterial  growth 
takes  place  in  the  same.  Even  a  slight  cooling  of  the 
butter  seems  to  be  of  benefit,  if  it  is  only  sufficiently 
prolonged.  Professor  Fjord,*  who  investigated  this  subject 
found  that  a  cooling  to  only  about  43°  F.  proved  sufficient  to 
check  the  spoiling  of  the  butter;  but,  says  Fjord,  "  it  must  be 
remembered  that  this  result  could  only  be  reached  when 
the  butter  was  cooled  from  the  time  it  was  packed  in  the 
creamery  to  within  two  or  three  days  before  the  scoring 
took  place.  If  such  cooling  take's  place  in  practice,  both 
creameries  and  the  railroads  and  the  steamers  should  have 
cooling-rooms  for  the  storage  and  shipment  of  the  butter." 

It  is  not  difficult  to-  arrange  for  the  proper  cooling  of 
the  filled  butter-tubs  in  our  creameries.  Ice-cellars  are 
also  found  on  most  farms  in  our  country  (butter  should 

*See  Eighth  Report  of  the  Copenhagen  Experiment  Station, 
"  On  the  Cooling  of  Butter,"  1888. 


THF   MANUFACTURE   AND   HANDLING    OF   BUTTER.    24? 

not,  however,  be  kept  in  the  same  room  as  other  articles 
of  food).  If  it  is  not  convenient  to  keep  the  butter  in 
these,  a  small  room  may  without  much  expense  be  fitted  up 
for  the  purpose  in  connection  with  the  ice-house.  The 
room  should  be  isolated  from  the  heat  of  the  surrounding 
air  in  the  same  way  as  the  ice-house,  by  means  of  sawdust 
or  similar  material.  It  may  also  be  advantageous  to  renew 
the  sawdust  every  year,  or  to  take  it  out  to  be  dried,  to 
prevent  the  spreading  of  fermentation-germs  and  to  de- 
crease its  heat-conducting  properties,  which  are  increased 
if  allowed  to  grow  wet.  A  Danish  cooling-room  which  I 
saw  was  adjoining  the  ice-house,  from  which  two  openings 
(about  8  inches  square)  were  made  into  the  cooling-room, 
one  near  its  ceiling,  the  other  near  the  floor.  The  cold  air 
from  the  ice-house  came  in  from  the  lower  opening,  and  the 
warmer  air  from  the  cooling-room  went  out  above.  By  this 
arrangement  the  cooling-room  was  kept  both  cool  and  dry. 

Transportation  of  Butter. — The  butter-tubs  must  be 
protected  against  being  heated  during  the  transportation 
to  the  railroad  station  or  steamboat.  This  is  especially 
important  where  the  factory  is  located  at  some  distance 
from  the  station.  To  avoid  this  heating  the  butter  should  not 
be  hauled  in  day-time  during  the  hot  season,  or  else  directly 
before  shipping,  and  the  hauling-wagons  should  be  provided 
with  a  double-walled  cover,  between  the  walls  of  which  dry 
bran,  saw-dust,  or  powdered  charcoal  may  be  packed. 

The  refrigerator-cars  run  on  our  railroads,  and  the  re- 
frigerator-rooms on  steamers,  are  of  the  greatest  service  to 
the  butter-producer.  The  benefit  derived  from  this  ar- 
rangement is,  however,  greatly  lessened  if  the  tubs  are  not 
properly  cared!  for  during  the  'hauling  to  and  the  delivery 
at  the  station.  A  reliable  driver  should  do  the  hauling, 


248  MODERN   DAIRY    PRACTICE. 

and  he  should  be  especially  instructed  to  guard  against  the 
heating  of  the  tubs.  The  latter  ought  not  to  be  taken 
from  the  wagon  too  early  and  should  preferably  go  directly 
from  the  wagon  into  the  refrigerator-car. 

Extractor  Butter. — The  extractor  butter  will  contain 
but  few  bacteria  if  the  milk  from  which  it  is  made  was 
produced  under  proper  conditions  of  cleanliness.  Besides 
the  advantages  of  the  separation  of  the  milk,  the  chances 
of  infection  of  the  cream  are  lessened  to  the  greatest  ex- 
tent possible.  It  is  a  sad  fact,  however,  that  the  short- 
comings of  the  extractor  seem  to  have  prevented  its  general 
applicability  up  to  the  present  time.  It  cannot,  of  course, 
be  used  for  the  manufacture  of  sour-cream  butter;  the 
sweet-cream  butter  made  by  the  extractor  seems  to  have  a 
tendency  to  softness  and  a  high  buttermilk  content. 
"  Paris  butter"  made  by  means  of  the  extractor  from  thor- 
oughly pasteurized  cream  is,  on  the  other  hand,  in  rny  ex- 
perience, of  the  highest  quality.  I  have  not  been  in  position 
to  make  any  investigation  of  the  keeping  qualities  of  the 
extractor  butter. 

The  Radiator  *  is  another  machine  by  means  of  which 
the  milk  can  be  made  directly  into  butter  (see  Fig.  30).  It 
is  manufactured  by  Aktiebolaget  Radiator,  Stockholm. 
This  apparatus,  which  I  have  had  occasion  to  test  criti- 
cally, has  proved  considerably  better  adapted  to  satisfy 
the  demands  for  good  sweet-cream  butter  possessing 
firmness  and  good  flavor  than  can  the  extractor.  The 
pasteurized  milk  is  separated  at  pasteurizing  temper- 
ature, by  which  method  a  good  yield  and  close  sep- 
aration is  obtained;  the  cream  is,  immediately  after  the 
separation,  cooled  in  the  apparatus  to  ordinary  churning 

*  Author's  addition  to  the  present  translation. 


THE   MANUFACTURE    AND    HANDLING   OF    BUTTER.    249 

temperature,  and  the  churning  is  then  conducted  by  a  very 
ingenious  arrangement.     The  fine  granular  butter  which 


FIG.  30. 

drops  from  the  apparatus  may  easily  be  worked  in  the 
ordinary  manner. 

Preservation  of  Butter. — Butter  being  an  expensive  and 
very  delicate  article  of  food,  it  has  of  course  been  the  ob- 
ject of  adulteration  and  admixtures  of  preservatives. 


250  MODERK   DAIRY   PRACTICE. 

Manetti  in  Milano  has  made  lengthy  experiments  to 
preserve  the  butter  by  exhausting  the  air  from  it.  It  was 
very  difficult  to  apply  the  method  to  practical  conditions, 
and  the  butter  assumed  a  spongy  consistency,  greatly  injur- 
ing its  commercial  value. 

Musso  and  Manetti  in  Lodi  state  that  an  admixture  of 
one  gram  salicylic  acid  to  one  kilogram  of  butter  is  able  to 
check  the  butyric-acid  fermentation  without  changing  the 
taste  and  appearance  of  the  butter,  and  they  direct  to  add 
the  acid  in  washing  the  butter.  According  to  Bersch  a 
salicylic-acid  solution  of  two  to  three  grams  salicyclic  acid 
per  liter  is  preferable  to  common  water  for  washing  the 
butter.  He  even  recommends  keeping  the  butter  in  such 
a  solution.  Boracic  acid  and  borax  have  also  been  recom- 
mended for  increasing  the  keeping  quality  of  butter,  but 
they  seem  to  give  it  a  bitter  taste. 

An  admixture  of  such  antiseptics  must,  however,  as 
previously  shown'  (p.  145),  be  considered  an  adulteration, 
especially  if  it  takes  place  without  the  knowledge  of  the 
buyer.* 

The  salting  of  the  butter  is  an  entirely  different  matter; 
the  fact  of  its  being  used  is  not  disclosed  for  the  public,  and 
each  buyer  may  easily  satisfy  himself  concerning  its  pres- 
ence. The  great  majority  of  people,  moreover,  demand  salt 
in  their  butter.  [The  same  applies  to  the  use  of  butter 
color  during  the  greater  portion  of  the  year. — W.] 

Canning  Butter. — Eather  than  applying  special  anti- 
septics, as  salicylic  and  boracic  acid,  etc.,  for  the  preserva- 
tion of  butter,  it  may  be  preserved  by  being  hermetically 

*  As  is  the  case  in  ninety-nine  cases  out  of  a  hundred  under 
present  conditions.  Concerning  the  admixture  of  preservatives  to 
food  articles,  see  p.  146,  foot-note.— W. 


THE   MANUFACTURE   AND   HANDLING   OF   BUTTER.    251 

sealed — a  method  which  has  long  been  practised,  especially 
in  case  of  butter  intended  for  exportation  to  the  tropics. 
Only  butter  of  the  very  best  quality  can  be  used  for  this 
purpose,  as  only  such  will  pay  for  the  additional  expense 
incurred  by  this  method,  and  only  such  butter  can  stand 
the  influence  of  the  long  transportation.  Both  sour-  and 
sweet-cream  butter  are  used  for  canning.* 

*  More  than  four  million  pounds  of  this  kind  of  butter  was  ex- 
ported from  Denmark  alone  during  the  year  1892-93. — W. 


CHAPTER  III. 
DISEASES  OF  BUTTER. 

IT  has  been  and  still  is  a  general  opinion  among  dairy- 
men that  a  great  many  of  the  various  diseases  of  butter  are 
attributable  to  a  faulty  feeding  of  the  cows.  But  it  has 
been  proved  by  bacteriological  investigations  that  many 
diseases  are  due  to  an  infection  of  the  milk,  cream,  or  but- 
ter with  one  or  more  forms  of  bacteria  producing  abnormal 
fermentations  in  the  same.  The  feeding  of  the  cows  cer- 
tainly influences  the  quality  of  the  butter,  as  has  been 
shown  in  a  large  number  of  older  experiments.  Other 
conditions  are  also  of  importance  in  this  regard.  Several 
butter  faults,  like  white-specked  butter  (arising  from  an 
excess  of  buttermilk  remaining  in  the  butter),  or  striped 
butter  (the  salt  being  unevenly  divided),  or  butter  showing 
an  uneven  color  in  the  tub,  etc.,  arise  as  a  result  of  faulty 
processes  of  manufacture.  A  smoky  smell  or  taste,  which 
is  sometimes  found,  especially  in  butter  from  small,  poorly- 
conducted  dairies,  is  caused  by  keeping  the  milk  or  cream 
in  impure  air.  Wood  taste  in  the  butter  arises  when  but- 
ter is  kept  in  tubs  either  made  from  an  unfit  kind  of  wood 
or  not  properly  cleaned,  etc. 

On  the  other  hand,  more  recent  investigations,  espe- 
cially by  the  Danes  Storch  and  Jensen,  show  that  a  great 
many  of  the  most  common  butter  diseases  have  their 
origin  in  an  infection  of  the  milk  or  cream  by  all  kinds  of 
bacteria. 

252 


DISEASES   OF   BUTTER.  253 

C.  0.  Jensen,  who  has  been  very  successful  in  his  stud- 
ies of  all  kinds  of  butter  diseases,  separates  these  diseases 
into  two  different  groups.  First,  diseases  caused  by  the 
presence  of  several  forms  of  bacteria,  which,  each  one  by 
itself,  is  harmless.  Second,  diseases  caused  by  the  presence 
of  a  single  definite  injurious  form  of  bacteria. 

"  Off  Flavor  "  in  Butter.— To  Group  I  the  butter  disease 
characterized  by  the  expression  an  "  off  "  flavor  and  taste  of 
the  butter  first  of  all  belong.  This  disease  springs  from  lack 
of  cleanliness  in  the  treatment  of  the  milk  and  the  cream. 
Jensen  is  correct  in  stating  that  the  fact  that  a  great  many 
forms  of  bacteria  and  a  multitude  of  each  of  them  are 
formed  during  the  ripening  of  the  cream  is  often  in  itself 
a  sufficient  reason  for  the  poor  quality  of  butter.  A  sample 
of  butter  examined  by  Jensen,  which  was  described  as  bitter, 
unclean,  dry,  and  soft,  contained  an  immense  number  of 
forms  of  bacteria  and  many  of  each  form.  The  disease  could 
not  be  ascribed  to  any  distinct  form  of  bacteria  present. 
The  numerous  foreign  bacteria  prevented  the  normal  lac- 
tic-acid fermentation,  and  i  is  also  possible  that  other 
decompositions  arose  in  the  cream  by  the  simultaneous 
presence  of  so  many  different  bacteria  forms  than  those 
produced  by  the  single  bacteria  forms  themselves. 

Among  the  diseases  of  Group  II  the  following  have 
been  investigated  at  the  present  time. 

1.  Tallowy  Butter. — In  his  investigations  and  experi- 
ments as  to  the  ripening  of  cream  Storch  found  a  lactic- 
acid  bacterium  to  which  he  ascribed  the  origin  of  this  dis- 
ease. This  bacterium  is  not  very  different  from  most  other 
lactic-acid  bacterium,  as^  far  as  size  and  form  go ;  but  if  al- 
lowed to  grow  luxuriantly  in  cream  during  its  ripening  it 
will  produce  a  most  disagreeable  tallowy  taste  in  the  butter 


254  MODERN    DAIRY    PRACTICE. 

made  from  it,  so  as  to  make  it  unpalatable  to  the  least  par- 
ticular palate. 

2.  Oily  Butter. — This    disease  is    characterized    by  a 
disagreeable  taste  and  smell  in  the  butter,  reminding  one 
of  ordinary  lubricating  oils.     Faulty  methods  of  working 
the  butter  or  of  feeding  (as  regards  the  composition  or  the 
quality  of  the  fodder)  are  often  given  as  causes.     Jensen's 
investigations  which  are  not  yet  furnished  show,  however, 
that  the  disease  is  caused  by  a  small  oval  bacterium  be- 
longing to  the  lactic-acid  bacteria,  which  produced  a  firm 
white  coagulum  in  the  milk  within  12-24  hours.     This  at 
the  same  time  assumed  a  disagreeable,  oily  odor.     The 
bacteria  thrived  best  at  about  77°  F.  (25°  C.);  at  ordinary 
room  temperature  it  developed  somewhat  more  slowly. 

3.  Root-taste  (Turnip-taste). — As  is  natural,  this  disease 
was  long  believed  to  be  due  to  a  too  liberal  feeding  of 
roots;   but  Jensen  has  shown  conclusively  that  the  ap- 
pearance of  disease  does  not  stand  in  any  relation  to  the 
method  or  system  of  feeding,  but  is  caused  by  one  or 
more  forms  of  bacteria  which  develop  in  the  milk  before 
or  during  the  ripening  of  the  cream.     In  a  sample  of  but- 
ter suffering  from  this  disease,  Jensen  isolated  a  staff -like 
bacteria  possessing  locomotive  power;   this  sample  origi- 
nated from  cows  that  were  not  fed  any  roots.     When  the 
bacteria  was  inoculated  into  milk  or  cream  it  caused  "  a 
disagreeable,  very  bitter  taste,  reminding  of  turnips  or 
rutabagas." 

4.  Rotten  Taste. — This  very  troublesome  disease  was 
mentioned  already  in  the  introductory  chapter  (see  p.  20). 
It  appeared  in  1888  at  Dueland  and  neighboring  farms 
(Denmark),  and  is  caused  by  a  bacterium  carefully  studied 
by  Jensen,  and  by  him  named   bacillus  fcetidus  lactis. 


DISEASES   OF   BUTTER.  255 

According  to  Jensen's  investigations  this  common  dis- 
ease seems  to  be  produced  through  the  activity  of  sev- 
eral distinct  bacteria;  first  among  these  a  small  oval  bac- 
teria appearing  in  groups  of  two  single  bacteria.  Inocu- 
lated into  milk  it  did  not  change  its  appearance,  but  within 
sixteen  to  twenty-four  hours  caused  a  distinct,  somewhat 
sweetish,  and  at  the  same  time  burnt  taste  and  flavor. 

6.  Bitter  Butter. — This  disease  seems  to  be  caused  by 
several  different  bacteria.     Conn*  isolated  a  micrococcus 
of  bitter  milk  in  an  American  sample  of  milk;  Weigmann 
in   Germany  speaks  of  a  bacillus  of  bitter  milk  which 
causes  a  bitter  butter,  but  does  not  injure  the  cheese  made 
from  the  milk.     A  third  bacterium  of  a  veritable  putrefac- 
tive form  has  in  my  experiments  shown  a  tendency  to 
make  both  milk  and  butter  bitter.     It  seems  to  thrive  sur- 
prisingly well  in  butter;  the  experiments  every  time  ended 
with  the  butter  practically  rotting  away. 

7.  Dappled  Butter. — This  disease  appears  rather  fre- 
quently in   farm  butter   during   the  summer,  the  butter 
being   dappled   by  grayish,  more  or  less   extended,  pale 
spots.     Danish  dairy  experience  tells  us  that  this  condi- 
tion is  caused  by  contamination  of  the  milk  in  the  stable, 
the  dairy,  or  during  the  milking.     This  is  correct  as  far  as 
the  location  of  the  trouble  is  concerned;  but  the  inner 
cause  of  the  disease  seems,  according  to  my  investigations, 
to  lie  in  the  activity  of  a  bacterium  possessing  a  high  loco- 
motory  power,  which  develops  in  the  butter,  spreading  in 
all  directions  from  small  separate  centres,  thereby  giving 
the  butter  a  mottled  appearance.     It  seems  to  possess  a 
smaller  vital  power  the  farther  it  is  removed  from  this 

*Storr's  Agr.  Experiment  Station  Report,  1891,  p.  158. 


256  MODERN   DAIRY   PRACTICE. 

center,  and  the  gray  color  will  gradually  disappear,  until  it 
is  entirely  gone.  This  bacteria  will  therefore  hardly  be 
able  to  spoil  larger  quantities  of  butter.  Neither  is  there 
any  difficulty  in  keeping  it  away  from  the  milk,  it  being 
unable  to  stand  even  a  heating  to  130°  F. 

8.  Blue   Butter.— This   disease  has  so  far  only  been 
found   in   Central   Europe.      It  appears  in  butter  made 
from  the  abnormal  milk  called  bluish  milk,  and  is  caused  by 
a  bacterium  (Bacillus  cyano  genus).*    The  Germans  Haub- 
ner  and  Fiirstenberg  and  the  Frenchman  Reiset  state  that 
they  have  frequently  met  with  such  blue  butter.     Haubner 
says,  however,  that  if  the  butter  was  well  prepared  and 
carefully  washed  the  blue  milk  would  not  produce  dis- 
eased butter,  but  only  in  case  of  a  greater  quantity  of  but- 
termilk remaining  in  the  butter.     I  have   also  been  in 
position  to  investigate  this  subject  and  have  corroborated 
Haubner's  results. 

9.  Moldy  Butter. — Butter  may  assume  a  moldy  taste 
and  flavor  also  in  other  cases  than  when  very  old.     I  have 
found  it  in  rather  fresh  butter  which  had  small  white 
specks  both  on  its  surface  and  in  the  inner  portion  of  the 
mass.     By  microscopic  examination  the  specks  proved  to 
be  mold-fimgi.     The  fungus  did  not  grow  on  any  of  the  nu- 
tritive substances  on  hand  at  that  time,  so  it  could  not  be 
further  studied.     Segelcke  met  with  moldy,  green-colored 
butter  in  1879. 

It  may  be  clear  from  the  preceding  accounts  of  the 
main  studies  and  investigations  at  hand  concerning  the 
production  and  keeping  of  milk  and  other  dairy  products 

*  See,  further,  "  Saprophytic  Micro-organisms  in  Cow's  Milk,"  p.  63. 


DISEASES   OF   BUTTER.  257 

that  dairying  in  our  days  is  no  more  a  single  trade,  but  is 
a  very  complicated  industry,  requiring  intelligent  workers, 
not  only  fully  familiar  with  the  manipulations  of  the 
dairy,  but  well  grounded  in  their  underlying  principles. 

The  fact  alone  that  the  raw  material  with  which  we 
have  to  deal  is  so  delicate  and  easily  changed  calls  into 
play  one's  highest  efforts  of  cleanliness;  there  are  so  many 
chances  of  harmful  bacterial  infection  in  the  various 
manipulations  that  thoughtfulness,  good  judgment,  and 
well-developed  power  of  observation  are  essentials  for  any 
dairyman. 

The  demands  made  on  farmers  and  dairymen  as  well  as 
all  dealers  in  dairy  goods  for  high-quality  products  have 
greatly  increased  of  late  years;  more  of  thorough  knowl- 
edge and  intelligent  understanding  is  required  than  ever 
before;  automatic  work,  no  matter  how  faithfully  per- 
formed, is  no  longer  in  keeping  with  the  greater  demands. 
The  words  spoken  by  Professor  Segelcke  more  than  ten 
years  ago  are  even  truer  to-day :  In  dairying  the  standard 
is  constantly  being  raised  higher  and  higher. 


?38^ 


PART  V.* 

CHEESE. 

CHAPTEE  I. 
BACTERIA  AND   CHEESE-MAKING. 

CHEESE  is  coagulated  and  pressed  casein  which  has 
undergone  certain  processes  of  fermentation.  Without 
fermentations  no  cheese;  without  bacteria  no  fermenta- 
tions; therefore  without  bacteria  no  cheese.  The  bacteria 
make  cheese  out  of  the  casein  and  give  it  the  characteristic 
flavor  desired  in  each  case.  We  owe  the  proof  of  the  cor- 
rectness of  these  statements  to  the  bacteriological  investi- 
gations conducted  during  late  years.  Before  1875  it  was 
believed  that  the  ripening  of  the  cheese  was  a  chemical 
process.  Cohn  first  maintained  that  this  view  was  incor- 
rect, and  that  the  ripening  is  attributable  to  the  vital  pro- 
cesses of  all  kinds  of  bacteria.  Decisive  proofs  have  later 
been  furnished  by  Duclaux,  Schaffer,  Bondzynski,  and  by 
Adametz. 

The    processes  of  fermentation  which  occur  in  the 

*  Author's  addition  to  American  translation. 

258 


BACTERIA    AND  CHEESE-MAKING.  259 

ripening  of  cheese  differ  in  various  kinds  of  cheese  and 
are  caused  by  different  forms  of  micro-organisms.  The 
intensity  and  duration  of  the  fermentations  are  also  differ- 
ent in  the  various  kinds.  The  soft  kinds  of  cheese  undergo 
violent  and  radical  fermentations,  while  certain  kinds  of 
English  cheese  ferment  only  slightly  and  very  slowly. 
We  find  a  smaller  number  of  bacteria  in  the  latter  kinds 
than  in  the  former.  Swiss  cheese  seems  to  stand  nearer 
the  soft  cheeses  as  regards  the  number  of  bacteria  con- 
tained in  it  and  the  intensity  of  the  fermentations,  but  it 
requires  a  rather  long  time  for  perfect  ripening. 

"What  dairy  science  at  the  present  time  knows  of  the 
bacteriology  of  cheese-making  is  due  above  all  to  the  inves- 
tigations of  Duclaux,  Adametz,  Weigmann,  and  v.  Freu- 
denreich.*  The  following  account  is  based  mainly  on  the 

*  The  following  references  include  the  main  investigations  of  the 
relation  of  bacteria  to  cheese- making  published  up  to  date  : 
ADAMETZ.     Ripening  of  Emmenthal  and  Cottage  Cheese.     Landw. 

Jahrb.,  18  (1893),  p.  227. 
The  Causes  of  Abnormal  Ripening  Processes  in  Cheese.    Milch- 

Zeitung,  1891,  pp.  237-248  ;  1892,  pp.  205-223. 
BAUMANN.    Studies  in  the  Ripening  of  Cheese.     Inaug.   Dissert. 

Univ.  Konigsberg,  1893  ;  Landw.  Versuchs.-Stat.,  42,  pp.  181- 

214 ;  Exp.  Sta.  Record,  5,  p.  249. 
BENECKE.    On  the  Causes  of  the  Changes  in  Emmenthal  Cheese 

during  Ripening.    Landw.  Jahrb.,  16,  p.  359. 
CONN.    Isolation  of  Rennet  from  Bacteria-cultures.     Storrs  School 

Experiment  Station  Report,  1892,  pp.  106-126. 
DUCLAUX.    Manufacture,  Ripening,  and  Diseases  of  Cantat  Cheese. 

Paris,  1878. 

Memoires  sur  le  Lait,  I-III.    Paris,  1880-84. 

Microbes  and  Fat.    Ann.  de  I'Inst.  Past.,  7  (1893),  pp.  305-324. 

FKEUDENREICH.     Ripening  of  Emmenthal  Cheese.    Landw.  Jahrb. 

d.  Schweiz,  4,  p.  17  ;  5,  p.  16  ;  Centralbl.  f.  Bakt.,  12,  p.  335. 


260  MODERN    DAIRY   PRACTICE. 

results  of  their  researches,  and  also  on  original  investiga- 
tions by  the  author. 

In  the  manufacture  of  cheese  the  casein  is  precipitated 
in  two  different  ways,  viz. : 

1.  By  means  of  certain  bacteria  producing  a  ferment 
which  coagulates  the  casein,  or 

2.  By  means  of  rennet. 

FREUDANREICH  Bacteria  causing  Formation  of  Holes  in  Cheese. 

Ann.  d.  Microgr.     2  (1890),  p.  353. 
The  Effect  of  Excluding  Air  in  the  Ripening  of  Emmenthal 

Cheese.    Landw.  Jahrb.  d.  Schweiz,  6,  p.  62 ;  Chem.  Centr.,  1893, 

No.  5. 
Experiments  in  Preventing  the  Formation  of  Holes  in  Cheese. 

Landw.  Jahrb.  d.  Schw.,  7,  p.  81. 
Causes  of  Bitter  Cheese.     Fuhling's  Landw.  Zeitung,  43  (1894), 

p.  361. 
GRAEFF.     Useful  and  Injurious  Bacteria  in  the  Manufacture  of 

Dutch  Cheese.    Molk.-ZeiL,  5,  p.  183. 
LEPIERRE.      Examination  of  a  Spoilt  Cheese.     Comptes  Rendus, 

1894,  p.  476. 
MCFADYEAN.     Chem.  Bact.  Investigation  of  a  Bacterium  Causing 

Inflammation  of  the  Udder  and  Formation  of  Holes  in  Cheese, 

Landw.  Jahrb.  d.  Schw.,  1890,  p.  64. 
MALENCHINI.     On  Ptomaines  in  Cheese.     Zeitschr.  /   Nahrungs- 

mittel  Unters.,  7  (1893),  p.  7. 

MANETTI  and  Musso.    On  the  Composition  and  Ripening  of  Par- 
mesan Cheese.    Landw.  Vers.-Stat.,  21  (1878),  p.  224. 
PAMMEL.    An  Aromatic  Bacillus  of  Cheese.    Bull.  No.  21,  Iowa 

Exp.  Station. 

Ripening  of  Cheese.    Ibid. 

WEIGMANN.     Formation  of  Holes  in  Cheese.    Landw.  Wochenblattf. 

Schl-HoL,  1890,  p.  890  ;  Landw.  Jahrb.,  20  (1890),  suppl.  1. 
Action  of  Rennet-producing  and  Peptouizing  Bacteria  in  the 

Ripening  of  Cheese.     Jahresb.  Kiel.  Milchw.  Inst.,  1892;  abstr. 

Molk.-Zeit.,  7,  p.  479.  — W. 


BACTERIA   AND   CHEESE-MAKING.  261 

Sour-milk  Cheese. — The  former  method  is  mainly  applied 
in  the  manufacture  of  so-called  sour-milk  cheese  ("  Dutch 
cheese  "),  prepared  by  the  spontaneous  souring  of  milk  and 
subsequent  heating,  by  which  processes  the  casein  is  com- 
pletely coagulated.  In  the  making  of  this  cheese  the  lactic- 
acid  bacteria  are  offered  as  favorable  conditions  as  possible. 
When  the  casein  is  precipitated  the  cheese  is  pressed,  and 
it  is  then  often  considered  ready  for  consumption.  At  some 
places  the  pressed  cheese  is  allowed  to  ripen  for  a  few  days, 
during  which  time  all  kinds  of  fermentations  arise.  The 
office  which  the  bacteria  fill  in  the  manufacture  of  this  cheese 
is  then  twofold:  (1)  the  casein  is  precipitated  and  (2)  the 
cheese  is  ripened  by  them.  In  the  former  work  only  lactic- 
acid  bacteria  take  part ;  in  the  latter  such  bacteria  appear 
as  use  the  casein  as  fermentation  material.  The  former 
decompose  the  milk-sugar  and  precipitate  the  casein  by 
the  ferment  which  they  produce;  the  latter  decompose  the 
precipitated  casein.  The  latter  group  of  bacteria  are 
usually  only  allowed  to  develop  to  a  limited  extent,  there 
being  otherwise  a  danger  that  the  fermentation  processes 
will  progress  too  far  under  the  very  favorable  conditions 
present,  in'which  case  the  bacteria  would  give  rise  to  harm- 
ful or  undesirable  fermentations,  producing  a  bad  flavor 
and  taste  in  the  cheese.  This  kind  of  cheese  will  therefore 
only  keep  for  a  short  period. 

The  sour-milk  cheese  is  the  oldest  kind  of  cheese  in 
Finland  (as  in  most  other  dairy  cduntries),  and  forms  an 
important  and  rich  article  of  food  on  the  table  of  most 
farmers.  Among  other  kinds  of  cheese  in  the  making  of 
which  the  lactic-acid  bacteria  play  an  important  part,  may 
be  mentioned  green  Swiss  cheese,  cottage  cheese,  etc. 

Cheese  Prepared  by  Means  of  Rennet.— Considering 


262  MODERN   DAIRY    PRACTICE. 

next  the  cheese  made  by  means  of  rennet,  we  may  first 
mention  that  rennet  forms  an  animal  ferment  prepared  in 
special  glands  in  the  third  stomach  of  calves.  In  the  co- 
agulation of  the  casein  by  means  of  rennet,  bacteria  as 
it  seems,  play  only  an  insignificant  part.*  Rennet  acts 
best  at  95°-104°  F.  (35°-45°  C.).  In  adding  the  rennet 
the  milk  is  heated  to  a  higher  or  lower  temperature  ac- 
cording to  the  time  in  which  the  coagulation  of  the  milk  is 
to  take  place. 

Among  the  kinds  of  cheese  belonging  to  this  group  we 
may  distinguish  between  two  subdivisions: 

1.  The  firm  cheeses,  requiring  a  long  ripening  period, 
in  the  curing  of  which  bacteria  play  the  main  part. 

2.  The  soft  cheeses,  requiring  a  short  period  of  ripening, 
the  curing  of  which  is  effected  not  only  by  bacteria,  but  by 
mold  fungi. 

The  manufacture  of  the  firm  cheese  is  very  complicated 
as  now  practised  in  cheese-factories;  as  we  shall  see,  the 
methods  followed  have  been  developed  from  experience. 
Let  us  take  a  glance  at  the  various  processes  in  order  to 
ascertain  what  part  the  bacteria  play  in  these. 

Methods  of  Manufacture  of  Firm  Cheese. — Milk  used  in 
the  manufacture  of  full  cream  cheese  is  usually  recently 
drawn  and  fresh.  Its  bacterial  content  is  as  a  rule  rather 
low,  but  it  is  of  course  by  far  not  germ-free.  Macroscopic 
as  well  as  microscopic  impurities  will  always  be  found  in 

*  The  small  number  of  bacteria  added  in  the  rennet  in  proportion 
to  those  already  present  in  the  milk  was  first  called  attention  to  by 
Bauinann  (Inaug.  Dissert.  Univ.  Konigsberg,  1893).  He  found  that 
under  ordinary  conditions  the  rennet  added  would  supply  only  one 
bacterium  for  every  two  thousand  already  present  in  the  milk.  See 
also  Pammel,  Bull.  21,  Iowa  Experiment  Station,  p.  799.— W. 


BACTERIA  AND   CHEESE-MAKING.  263 

it.  Concerning  the  macroscopic  impurities  of  milk,  see 
p.  31.  The  microscopic  impurities  are  numerous  and  indi- 
cate contamination  of  dust  or  dung-particles  in  the  stable. 
In  the  making  of  certain  kinds  of  Dutch  cheese  it  is  con- 
sidered of  primary  importance  that  the  milk  be  removed 
from  the  stable  as  quickly  as  possible,  and  that  it  be  coag- 
ulated while  still  warm  from  the  cow.  Those  acquainted 
with  the  care  and  cleanliness  maintained  in  Dutch  stables 
will  know  that  these  cheeses  are  prepared  from  a  compara- 
tively pure  milk. 

Eennet  and  cheese-color  are  first  added  to  the  milk. 
The  former  coagulates  the  casein,  entangling  in  it  all  ma- 
croscopic impurities  along  with  microscopic  ones  adhering 
to  them,  and  also  retaining  the  bacteria  suspended  in  the 
milk.  The  bacteria  thus  inclosed  in  the  coagulated  casein 
come  from  three  different  sources,  viz. :  (1)  from  the  milk 
and  its  impurities;  (2)  from  the  rennet — which,  especially  if 
prepared  from  calves'  stomachs  at  the  cheese-factory,  usually 
contains  an  immense  number  of  bacteria  (rennet  extract 
contains  a  small  number  of  bacteria*);  and  (3)  from 
the  cheese-vat  and  the  air.  In  the  beginning  these  bac- 
teria seem  to  play  an  insignificant  part,  and  in  some 
kinds  of  cheese  the  increase  takes  place  but  slowly.  We 


*  The  number  of  bacteria  in  rennet  extract  has  been  determined 
by  Baumann  and  Pammel.  The  former  (loc.  cit.)  found  in  two 
samples  of  rennet  tablets  39,250  bacteria  per  cc.  (strength  1 :  200,000) 
and  32,400  bacteria  per  cc.  (strength  1 :  32,000) ;  a  sample  of  Danish 
fluid  extract  contained  1,407,600  bacteria  per  cc.  (strength  1 :  5000). 
Pammel  and  students  working  with  him  found  in  five  determina- 
tions of  the  bacteria  content  of  fluid  rennet  extracts  from  409,500 
to  4,019,200  bacteria  per  cubic  centimeter.— W. 


264  MODERN   DAIRY   PRACTICE. 

shall  see  directly,  however,  that  they  soon  make  their  pres- 
ence felt.  In  some  kinds  of  cheese  it  is  considered  im- 
portant that  the  coagulation  takes  place  rather  slowly,  in 
40  to  50  minutes,  and  the  temperature  during  the  same  is 
increased  from  about  86°  to  104°-131°  F.,  a  temperature 
especially  favorable  to  certain  forms  of  bacteria.  It  is 
then  cut  and  run  through  a  curd- mill,  and  the  whey  is  re- 
moved. 

Some  kinds  of  cheese  require  that  the  curd  be  kept 
warm  continually,  so  that  it  will  rapidly  turn  acid,  by 
which  means  it  assumes  a  distinct  sour  taste  and  flavor;  it 
is  often  also  considered  advantageous  to  continue  the 
heating  even  in  the  press.  In  this  way  highly-favorable 
conditions  of  temperature  are  for  several  hours  offered  the 
bacteria  in  the  curd.  There  is  plenty  of  moisture,  and  the 
casein  as  well  as  the  milk-sugar  are  excellent  nutritive  sub- 
stances for  bacteria;  these  therefore  multiply  rapidly  in  the 
curd.  The  action  of  the  bacteria  is  shown  from  the  fact 
that  in  nearly  all  kinds  of  cheese  we  observe  during  the 
first  twenty-four  hours  small  holes  throughout  its  mass. 
In  some  kinds  the  holes  soon  disappear;  in  others  they 
remain  and  sometimes  even  grow  larger.  They  arise  on 
account  of  a  gas  generation  (especially  carbonic-acid  gas*) 
caused  by  certain  bacteria,  butyric-  and  lactic-acid  bac- 
teria being  the  main  ones.  This  fermentation  generally 
belongs  to  the  normal  changes  in  the  cheese.  If  the  de- 
sirable forms  of  bacteria  are  not  present,  or  are  present  in 

*  According  to  Baumann  the  gases  causing  holes  in  cheese  con- 
sist mainly  of  carbonic  acid  (63  per  cent)  and  hydrogen,  and  also 
small  quantities  of  other  gases,  but  no  hydrocarbons.  (Landw. 
Vers.  Stat.,  42,  p.  214).  See  also  Adametz,  MUch-Zeitung,  1893, 
p.  220.— W. 


BACTERIA  AND   CHEESE-MAKING.  265 

too  small  a  number  compared  with  the  others,  troublesome 
cheese-diseases  may  arise  even  in  the  first  stages  of  the 
manufacture.  Freudenreich  thus  isolated  a  bacteria  which 
caused  irregular  cracks  in  Swiss  cheese  (gebldhter  Kdse) 
or  else  an  immense  number  of  irregular  holes  (Nissler 
Kdse),  giving  the  cheese  a  different  appearance  than  that 
produced  by  the  desired  regular  holes.  He  states  that  if 
this  micro-organism  is  inoculated  into  the  milk,  and  cheese 
at  once  made  from  it,  the  comparatively  few  bacteria  will 
cause  the  appearance  of  large  irregular  holes  (the  first- 
mentioned  disease);  but  if  the  bacteria  are  allowed  to 
multiply  in  the  milk,  i.e.,  if  it  is  left  to  coagulate  slowly, 
the  second  form  of  the  disease  will  arise. 

In  some  kinds  of  cheese,  e.g.  certain  English  cheese 
where  a  slow  fermentation  and  a  solid,  closed  cheese  is 
wanted,  the  curd  is  salted.  Besides  checking  the  growth 
of  the  bacteria  this  gives  to  the  cheese  the  salt  taste  de- 
sired. In  other  kinds,  e.g.  Swiss  cheese,  the  first  fermen- 
tation is  left  to  continue  unchecked,  and  the  salting  does 
not  take  place  until  the  cheese  has  been  pressed. 

Curing  of  Cheese. — After  having  been  put  into  molds 
and  pressed,  the  cheese  is  ready  for  the  curing  process  in 
which  it  is  to  assume  the  flavor  desired.  For  this  purpose 
the  cheese  is  brought  either  into  the  curing-room  or  di- 
rectly into  the  cheese-cellar,  according  to  the  demands  in 
each  case.  The  cheese  in  the  former  case  is  allowed  to 
dry  out  somewhat  in  the  fairly  dry,  pure  air  of  the  curing- 
room  and  is  then  transferred  to  the  cheese-cellar,  where 
the  curing  proper  will  take  place.  The  most  important 
work  which  the  bacteria  have  to  perform  in  the  cheese 
then  begins. 


266  MODERK   DAIRY   PRACTICE. 

The  curing  consists  of  a  series  of  different  fermenta- 
tions which  succeed  one  another  and  are  caused  by  dif- 
ferent kinds  of  bacteria  appearing  one  after  the  other. 
Duclaux  first  gave  a  scientific  account  of  this  phenomenon 
in  his  in  several  respects  remarkable  work  on  milk  entitled 
"Le  Lait,  Etudes  Chirniques  et  Microbiologiques."  In  the 
Cantat  cheese,  manufactured  in  southern  France,  he  found 
not  less  than  ten  different  kinds  of  bacteria  during  its  period 
of  curing,  seven  of  which  were  aerobic  and  three  ana- 
erobic. The  statement  made  of  the  action  of  the  different 
bacteria  is  briefly  as  follows  :  Some  of  the  bacteria  pro- 
duce both  a  rennet-like  substance,  the  object  of  which  is 
unknown,  and  a  ferment  which  changes  the  casein  to  a 
soft  consistency  characteristic  of  the  ripe  cheese.  Other 
bacteria  continue  the  work  of  the  curing  and  give  rise  to 
strong-smelling,  often  sharp  fermentation  products,  which 
finally  may  be  still  further  changed  by  other  bacteria  and 
decomposed  into  leucin,  ammonia,  etc.  Weigmann  has 
also  isolated  this  ferment  (casease)  and  shown  its  great 
importance  in  the  curing  of  the  cheese. 

Adametz  investigated  Swiss  cheese  (Emmenthaler)  and 
Swiss  cottage  cheese  (Hauslcdse)  belonging  to  the  soft 
kinds  of  cheese  to  be  considered  later  on,  and  found  in 
them  an  enormous  number  of  bacteria,  of  nineteen  dif- 
ferent forms,  which  he  refers  to  three  separate  groups. 
The  bacteria  of  the  first  group  are  not  able  to  dissolve  the 
casein,  but  change  it  to  a  characteristic  jelly-like  consist- 
ency which  later  is  easily  attacked  by  other  bacteria  and 
subjected  to  farther  changes.  Micro-organisms  of  the 
second  group  continue  where  the  first  group  left  off  and 
are  unable  to  attack  the  original  curd.  The  bacteria  of 


BACTERIA   AND   CHEESE-MAKING.  267 

the  third  group  are  indifferent.  In  the  curing  of  the 
Roquefort  cheese  certain  molds  play  an  important  part.* 

The  number  of  bacteria  contained  in  cheese  increases 
immensely  during  the  curing  process.  At  its  beginning 
Adametz  found  90,000  bacteria  in  one  gram  of  Swiss 
cheese,  but  when  the  fermentation  was  at  its  highest  as 
many  as  850,000  were  found  in  it.  By  adding  small 
quantities  of  disinfectants  to  the  cheese,  Adametz  pre- 
vented the  bacteria  in  the  cheese  from  increasing,  but  at 
the  same  time  the  curing  process  of  the  cheese  was  com- 
pletely checked.f 

Method  of  Manufacture  of  Soft  Cheese. — In  most  of 
the  firm  kinds  of  cheese  spoken  of  in  the  preceding,  the 
curing  process  takes  place  very  slowly;  in  some  it  lasts  for 
a  year,  in  others  for  several  years.  In  the  soft  kinds  of 
cheese,  on  the  other  hand,  the  curing  has  a  much  more 
rapid  course.  The  coagulated  and  molded  curd  is  highly 
infected  by  placing  the  green  cheese  on  straw  mats  pre- 
viously used,  in  a  room  where  molds,  etc.,  are  plentiful. 
Before  long  the  cheeses  will  be  spotted  with  brown  mold 
colonies  which  gradually  spread  to  a  white  downy  cover. 
At  the  same  time  the  bacteria  in  the  cheese  have  started 
their  fermentations,  but  the  relatively  low  temperature 

*  Roquefort  cheese  is  made  in  the  department  of  Aveyron, 
southern  France,  from  sheep's  milk.  Carefully-prepared  molded 
bread  is  introduced  in  the  forms  between  the  layers  of  curd,  and 
the  cheese  is  ripened  in  mountain-caves,  where  the  temperature  is 
very  low  and  varies  but  little  (39°-46°  F.),  while  the  air  is  kept 
exceedingly  moist  by  small  streams  of  water  running  down  the  walls 
of  the  caves  (relative  humidity  about  60°). — W. 

fSee  also  Pammel  (Bulletin  No.  21,  Iowa  Experiment  Station, 
p.  798)  and  Baumann  (loc.  cit.). — W. 


268  MODERH    DAIRY    PRACTICE. 

retards  their  progress,  while  molds  thrive  and  act  011  the 
cheese.  After  sometime  the  mold  vegetation  assumes  a 
bluish  color,  and  the  color  of  the  cheese  turns  reddish 
yellow.  If  the  air  grows  too  moist,  these  molds  will  die 
and  the  putrefactive  bacteria  will  take  their  place,  thus 
spoiling  the  cheese.  If  sunlight  strikes  the  molds,  they 
will  also  die  and  fermentations  are  stopped.  After  some 
time — e.g.,  with  the  Camembert  cheese  in  twenty-five  days 
—the  cheese  is  brought  from  the  curing-room  into  the 
cheese- cellar,  which  is  usually  built  half  underground  and 
so  arranged  that  its  temperature  will  remain  fairly  constant 
at  54°-5?°  F.  (12°-14°  C.),  and  that  direct  sunlight  and 
draught  are  avoided.  The  activities  of  the  molds  are  here 
soon  checked  and  the  work  of  the  bacteria  proper  begins. 
These  are  now  in  position  to  multiply  immensely. 
Adametz  found  the  usual  bacteria  content  of  Swiss  cot- 
tage cheese  (Hauskdse)  2-5  millions  per  gram. 

At  the  present  stage  of  our  knowledge  of  the  action  of 
bacteria  in  the  curing  of  cheese  it  would  hardly  be  advis- 
able to  give  a  more  detailed  account  of  the  morphology 
and  other  characteristics  of  the  separate  cheese-bacteria 
which  have  so  far  been  identified.  There  are  still  many 
points  in  the  complicated  processes  of  manufacture,  and 
especially  in  the  curing  of  cheese,  which  are  not  yet 
worked  out,  and  the  nature  of  several  of  the  bacteria  iso- 
lated have  not  been  sufficiently  studied  in  detail.  About 
fifty  different  forms  are  at  the  present  included  among 
the  so-called  cheese-bacteria,  and  this  number  will  doubt- 
less be  considerably  increased  when  further  study  has  been 
made.  In  the  curing  of  different  kinds  of  cheese  different 
forms  of  bacteria  are  evidently  at  work.  Of  the  ten  forms 
of  bacteria  which  Duclaux  found  active  in  the  curing  of 


BACTERIA   AND   CHEESE-MAKING.  269 

Cantat  cheese,  not  a  single  form  is  present  in  Swiss  cheese, 
as  shown  by  Adametz's  investigations.  In  my  work  with 
Swiss  cheese  made  in  Finland  I  have  found  but  very  few 
of  the  bacteria  which  the  latter  scientist  gives  as  typical 
for  this  cheese. 

All  the  methods  of  cheese-manufacture  so  far  described 
are  characterized  by  the  fact  that  although  the  bacteria 
play  a  most  important  part  in  the  making  and  curing  of 
the  cheese  in  each  case,  no  special  care  is  taken  that  the 
desired  bacteria  are  really  introduced.  It  is  left  to  chance 
whether  they  take  part  or  not.  Often,  however,  the  out- 
come is  different  than  was  expected,  the  cheese  produced 
having  a  different  flavor  and  being  of  a  different  appear- 
ance than  that  desired.  I  shall  only  mention  that  the 
Swiss  scientist  Freudenreich  states  that  40  per  cent  of  Em- 
menthol  cheese  is  not  cured  in  the  proper  manner,  and 
that  we  still  more  rarely  find  the  correct  flavor  and  taste 
in  imitation  Swiss  cheese.  The  same  is  true  in  case  of 
the  soft  French  cheeses.  Outside  of  their  native  country 
they  only  exceptionally  obtain  the  genuine  flavor  and  ap- 
pearance. 


CHAPTER  II. 
OLD-METHOD  CHEESE-MAKING. 

IT  has  always  been  considered  a  maxim  in  dairying 
that  the  manufacture  of  cheese  differs  from  butter-making 
in  this  respect,  that  while  cleanliness  is  the  fundamental 
rule  in  the  latter,  it  may  safely  be  left  out  of  sight  in 
the  former.  Lack  of  cleanliness  has  even  by  some  people 
been  considered  an  essential  point  in  the  management  of 
cheese-factories,  and  the  mountain  factories  of  the  Swiss 
have  been  offered  as  proof  of  the  correctness  of  this  state- 
ment. Everywhere  in  these  cheese-factories,  as  I  have 
had  occasion  to  personally  ascertain,  conditions  incompati- 
ble with  cleanliness  are  met  with,  although  not  to  the 
same  extent  in  the  large  new  cheese-factories  as  in  the 
small  Alp  factories.  At  the  latter  the  barn  usually 
directly  adjoins  the  cheese  building;  a  calf-stable  may 
even  be  found  in  the  cheese  building,  with  calves  in  it; 
both  the  walls  and  the  ceiling  of  the  room  are  black  and 
dirty;  only  dirt  floors  are  usually  found,  and  frequently 
the  fireplace  lacks  a  good  chimney  and  the  smoke  finds 
its  way  out  wherever  it  can,  through  cracks  in  the  walls 
and  ceiling.  Similar  conditions  are  found  in  the  curing- 
room  and  the  intense  smell  in  the  latter  plainly  indicates 
that  numerous  fermentations  take  place  there. 

Neither  is  special  cleanliness  observed  in  the  manufac- 
ture of  soft  French  cheeses,  as  may  easily  be  ascertained. 

270 


OLD-METHOD   CHEESE-MAKING.  271 

Molds  thrive  luxuriously  on  the  shelves  and  walls  in  the 
curing-room,  and  are  not  removed  therefrom  ;  no  care  and 
neatness  are  observed  in  the  milking  and  the  early  treat- 
ment of  the  milk.  And  in  spite  of  all  lack  of  cleanliness 
excellent  cheese  is  made. 

In  case  of  English  or  Dutch  cheeses  a  somewhat  dif- 
ferent practice  is  followed.  Cleanliness  is  observed  at 
least  in  the  manufacture  of  the  cheese,  although  not  even 
here  is  it  always  considered  absolutely  essential  in  order 
to  obtain  good  products.  Especially  in  the  curing-room 
or  cellar  it  is  often  preferred  that  certain  molds  attack 
the  cheese. 

It  may  furthermore  be  noted  as  characteristic  of  the 
manufacture  of  cheese  that  its  theory  has  only  to  a  small 
extent  been  worked  out.  It  has  been  an  art  in  which  it 
has  been  necessary  in  the  main  features  to  blindly  "  follow 
the  steps  of  our  forefathers/'  without  knowing  why  it  is 
done  this  and  "not  that  way.  In  the  manufacture  of 
certain  kinds  of  cheese,  as,  e.g.,  the  Swiss  cheese,  the 
experience  of  centuries  has  accumulated  from  generation 
to  generation.  One  has  not  deviated  a  hair's  breadth 
from  the  paternal  inheritance,  for  otherwise  "  the  cheese 
would  not  be  good."  No  other  explanation  was  given  or 
can  be  given. 

The  old-method  cheese-making  is  in  many  ways  analo- 
gous to  the  old-method  butter-making.  In  both  we  act 
according  to  old  custom;  in  both  the  fermentations  are 
started  without  knowing  their  nature  or  without  any  cer- 
tainty of  the  outcome.  The  fermentations  in  the  former, 
being  less  radical  and  far  less  complicated,  are  more  easily 
reached.  In  the  old-method  cheese-manufacture,  on  the 
other  hand,  much  more  complicated  processes  of  fermenta- 


272  MODERN   DAIRY   PRACTICE. 

tion  take  place,  and  we  cannot  therefore  make  use  of  such 
simple  means  as  in  butter-making.  To  reach  the  desired 
changes  in  the  cheese,  it  was  necessary,  where  these  are 
rather  energetic,  to  give  up  cleanliness,  and  a  more  intense 
infection  with  fermentation  bacteria  was  thus  secured. 
Where  less  thorough  changes  are  needed,  as,  e.g.,  in  the 
making  of  English  or  Dutch  cheeses,  greater  cleanliness 
can  be  observed,  but  cleanliness  is  not  even  here  observed 
to  any  similar  extent,  as  we  have  seen,  as  is  necessary  in 
the  manufacture  of  butter. 

It  is  but  natural  that  successful  results  are  often  not 
obtained  when,  as  is  often  the  case,  several  kinds  of  cheese 
are  made  in  the  same  factory  and  kept  in  the  same  curing- 
room.  We  saw  that  the  different  kinds  of  cheese  need 
different  bacteria  for  their  proper  curing,  and  different  de- 
grees of  moisture  and  temperature,  etc.,  and  still  they  are 
made  to  cure  in  the  same  room  and  it  is  expected  that 
each  will  develop  its  characteristic  flavor.  The  result  usu- 
ally is  that  the  different  kinds  are  all  failures. 

If  we  compare  such  cheese-factories  with  those  in 
Switzerland,  we  find  at  once  that  the  old  method  of  cheese- 
manufacture  in  the  latter  country  is  on  a  considerably 
firmer  basis  than  that  elsewhere.  Only  one  kind  of 
cheese  is  usually  made  in  Switzerland,  and  it  has  been 
manufactured  through  centuries.  All  curing-rooms,  cheese- 
factories,  and  perhaps  also  farm-houses  have  been  infected 
with  the  very  bacteria  favorable  to  the  curing  of  this 
cheese,  and  it  is  therefore  almost  a  certainty  that  the  correct 
bacteria  will  appear  to  ripen  the  cheese  in  the  manner  de- 
sired.* In  the  same  way  every  section  of  France  makes 

*Baumann  (Landw.  Vers.  8tat.,  42,  p.  214)  states  that  the  fact 
that  genuine  Emmenthal  cheese,  i.e.,  such  made  in  Switzerland  it-- 


OLD-METHOD   CHEESE-MAKING.  273 

mainly  one  kind  of  cheese,  and  it  is  natural  that  the  bac- 
teria useful  in  each  case  under  such  conditions  must 
gradually  obtain  the  upper  hand. 

We  may  in  this  connection  mention  a  practice  which  I 
have  been  informed  has  been  followed  at  a  German  cheese- 
factory  in  order  to  start  the  correct  fermentation  in  the 
soft  "French  cheese."  When  the  factory  was  opened, 
some  green  cheese  guaranteed  to  be  genuine,  was  im- 
ported from  France.  The  whole  factory  was  then  in- 
fected with  this  cheese,  the  cheese-room  and  the  vats, 
the  curing-room,  cellar,  and  especially  the  shelves  in  the 
rooms,  etc.  When  cheese  was  later  carefully  made  accord- 
ing to  the  directions  given,  the  curing  process  desired,  and 
an  excellent  quality  was  secured  in  the  product.  Such  a 
method  of  mass-infection  is  a  step  toward  new-method 
cheese-making — toward  the  cheese-making  of  the  future. 

self,  is  better  than  that  made  elsewhere,  is  due  not  so  much  to  the 
aromatic  feed  which  the  cows  find  in  the  mountain  pastures  or  in  a 
higher  fat  content  of  the  Swiss  milk,  as  to  the  number  of  different 
forms  of  bacteria  in  the  milk  being  subject  to  smaller  changes,  and 
the  process  of  manufacture  followed  being  better  suited  to  the  mix- 
ture of  bacteria  in  the  milk,  than  is  elsewhere  the  case.— W. 


CHAPTER  III. 
NEW-METHOD  CHEESE-MAKING. 

THE  fact  that  fermentations  will  always  take  place  in 
the  cheese  no  matter  what  the  method  of  manufacture  fol- 
lowed, would  at  first  thought  seem  to  indicate  that  there 
can  hardly  be  any  improvement  in  conducting  the  cheese- 
making  on  a  systematic  basis.  "  Fermentation-starters  are 
found  everywhere,  and  we  cannot  force  forward  the  fer- 
mentation wanted  " — these  are  the  arguments  with  which 
old-method  cheese-makers  try  to  silence  the  efforts  of  im- 
provement. Several  facts  are,  however,  now  known  which 
throw  a  doubt  on  the  correctness  of  these  assertions.  The 
example  just  given  of  the  mass-infection  introduced  at  the 
German  cheese -factory  shows  the  possibility  of  a  rational 
system  of  cheese-making.  The  same  objections  were  of- 
fered against  the  use  of  pure  cultures  in  other  fermenta- 
tion industries,  and  these  have  here  been  shown  entirely 
feasible.  In  the  making  of  sour-cream  butter  the  old 
method  of  spontaneous  ripening  of  the  cream  had  to  yield 
to  modern  methods  of  using  starters  or  pure  cultures,  and 
in  the  manufacture  of  beer  the  progress  made  by  the  intro- 
duction of  modern  methods  has  been  equally  pronounced. 
We  cannot  overlook  the  fact  that  the  manufacture  of 
cheese  is  considerably  more  complicated  than  the  industries 
just  mentioned,  but,  on  the  other  hand,  practical  laboratory 

274 


NEW-METHOD   CHEESE-MAKING.  275 

experiments  have  already  shown  that  the  case  is  not  hope- 
less. 

Instead  of  following  the  method  of  controlling  the  fer- 
mentation processes  in  the  cheese  through  a  "  mass-infec- 
tion," another  may  be  practised  which  leads  to  a  more 
successful  result,  viz.,  the  introduction  of  pure  cultures, 
the  milk  being  pasteurized  and  strict  cleanliness  being  ob- 
served throughout  the  manufacture.  The  main  points  in 
this  method  of  manufacture,  which  we  may  call  new- 
method  cheese-making,  are  considered  in  the  following. 

1.  Pure,  Clean  Milk. — Such  milk  is  obtained  through 
a  careful  observation  of  the  directions  given  in  the  early 
part  of  this  work  as  to  cleanliness  in  the  stable  and  in  the 
hauling  of  the  milk,  and  by  pasteurization  of  the  same. 
If  the  milk  has  not  become  highly  infected  with  bacteria 
in  the  stable,  even  a  slight  heating  may  be  of  service  for 
the  annihilation  of  the  bacteria.    Freudenreich  has  by  prac- 
tical experiments  shown  the  great  benefit  of  pasteurization 
in  the  manufacture  of  cheese.     The   cheese  made  from 
pasteurized  milk  did  not  cure  on  account  of  the  small 
number  of  bacteria  contained  in  it;  not  until  the  milk 
was  inoculated  with  certain  bacteria  could  the  curing  take 
place.     The  pasteurized  milk  demands  special  methods  for 
the  making  of  cheese,  as  cooling  after  the  heating,  use  of 
larger  quantity  of  rennet  extract,  etc. 

2.  Exclusion  of  Injurious  Infection  from  the  Surround- 
ings.— The  main  condition  for  the  exclusion  of  harmful 
infection    from    the    surroundings   is  cleanliness  in  the 
factory  and  in  the  factory  men.      If    the  objects  sur- 
rounding the  milk  are  kept  sufficiently  clean,  there  will 
be  no  danger  in  this  direction.     There  is  no  need  of  entire 
exclusion  of  all  infection,  as  any  small  number  of  harmful 


276  MODERN    DAIRY    PRACTICE. 

bacteria  possibly  present  in  the  cheese  may  easily  be  over- 
powered by  the  larger  number  of  bacteria  added  in  the 
direct  infection.  The  milk  is  coagulated  in  carefully- 
cleaned  vats,  and  the  cutting  of  the  curd,  the  milking, 
pressing,  and  other  processes  in  the  manufacture  take 
place  as  rapidly  and  in  as  cleanly  manner  as  possible. 
The  Dutch  and  English  cheese-factories  in  many  respects 
come  up  to  the  demands  made  in  the  preceding. 

3.  Direct  Infection. — Experiments  have  been  made  by 
several  scientists  for  the  preparation  of  pure  cultures  for 
curing  of   cheese,  but  so  far  with  only  partial  success. 
The   difficulties  met  with  in  this  case  are  considerable. 
We  do  not  here  have  only  one  or  two  kinds  of  bacteria  in 
pure  cultures,  as  is  the  case  in  the  brewing  of  beer  or  in 
the  manufacture  of  sour-cream  butter,  but  as  the  assist- 
ance of  several  kinds  of  bacteria  are  necessary  in  the  mak- 
ing of  cheese,  we  must  obtain  pure  cultures  of  several  forms 
to  obtain  a  proper  curing  of  the  cheese.     This  part  of  new- 
method  cheese-making  is  yet  at  the  stage  of  experimenta- 
tion, but  the  investigations  at  hand  at  the  present  give 
certain  hope  of  the  solution  of  the  problem.     We  shall  not 
here  go  farther  into  a  discussion  of  this  question  or  explain 
the  practical  methods  for  the  applications  of  such  pure 
cultures,  as  these  are  still  not  sufficiently  worked  out,  or 
have  not  yet  been  subjected  to  tests  in  practical  operations. 

4.  Clean  Cheese-cellar. — By  cleanliness  in  the  cheese- 
cellar  we  do  not  understand  the  same  as  is  usually  meant 
by  the  work  in  modern   dairying.     It  is  not  so  much  a 
question  of  having  a  cellar  where  no  bacteria  are  found  as 
a  cellar  where  only  those  favorable  for  the  curing  of  cheese 
are  found.     To  reach  this,  both  disinfection  and  infection 
must  be  practised;   the  former  in  order  to  destroy  the 


HEW-METHOD   CHEESE-MAKING.  277 

harmful  bacteria  possibly  present  in  the  cellar,  and  the 
latter  to  introduce  the  useful  ones. 

The  new  method  of  cheese-making  still  lacks  a  good 
many  accessories  and  is  but  little  tried  in  practice,  but  it 
is  in  several  respects  beginning  to  break  its  way.  All 
kinds  of  publications  and  specific  laboratory  experiments 
and  even  smaller  cheese-factory  experiments  give  promise 
that  the  necessary  accessories  and  methods  will  not  be 
long  in  coming.*  It  is  also  doubtless  a  fact  that  definite 
systematic  methods  of  cheese-making  are  absolutely  neces- 


*  Detailed  accounts  of  the  various  kinds  of  cheese  and  more  or 
less  complete  directions  for  their  manufacture  will  be  found  in  the 
following  works,  which  include  our  best  literature  on  the  subject  of 
cheese-making : 

KLENZE.    Handbuch  d.  Kaserei-Technik.    Bremen,  1884.     643  pp. 
ENGLING.     Kleines  Handbuch  d.  prakt.  KHserei.    Bremen,  1892. 

252  pp. 

DECKER.    Cheddar  Cheese-making.    Madison,  Wis.,  1893.    118pp. 
MARTINY.     Die  Milch,  II.     Danzig,  1871.    pp.  200-281. 
SHELDON.     Dairy  Farming.     Cassell  &  Co.,  New  York  and  London. 

pp.  196-283. 
HARRIS.    Cheese-  and  Butter-maker's  Handbook.    Glasgow,  1885. 

pp.  21-87. 
FLEISCHMANN.    Das   Molkereiwesen.     Braunschweig,  1876.     pp. 

735-1027. 

Lebrbuch  d.  Milchwirtschaft.    Bremen,  1893.    pp.  175-251. 

KIRCHNER.     Handbuch  d.  Milch wirtschaftv    3d  ed.    Berlin,  1891. 

pp.  389-501. 

WAGNER.    Milch,  Butter  und  Kase.     Weimar,  1881.     pp.  184-291. 
OTTO.    Die  Milch  und  ihre  Produkte.     Berlin,  1892.    pp.  127-169. 
DUCLAUX.     Le  Lait.     Paris,  1887.     pp.  63-311. 

Principes  de  Laiterie.     Paris,     pp.  269-361. 

LEZE.    Les  Industries  du  Lait.    Paris,  1891.    pp.  429-633. 


V     OF  ra 
TWrTTWr 


MODERN    DAIRY    PRACTICE. 

sary  in  our  dairy  practice.  The  great  uncertainty  in  the 
present  methods  and  their  varying  results  makes  the  manu- 
facture of  cheese  a  risky  and  expensive  industry.  By  the 
introduction  of  more  rational  methods  good  results  will  be 
obtained  with  greater  certainty;  the  cheese  will  be  forced 
into  exactly  the  desired  fermentations,  thereby  decreasing 
the  number  of  unsuccessful  cheeses  manufactured  and 
making  the  cheese  produced  both  cheaper  and  of  a  better 
quality. 


INDEX. 


PAGE 

Abnormal  milk 44 

Acid  starters,  use  of,  in  cream-ripening 215 

Aeration  of  milk 63 

Airing  factory  utensils 119 

Amphoteric  reaction  of  milk 45 

Arnold  steam  sterilizer ,  16 

Baby-feeding,  milk  for 159 

Bacilli,  definition  of 2 

Bacteria,  aerobic,  definition  of 11 

anaerobic,  definition  of 11 

and  air 11,51 

cheese-making 258 

literature  on 259 

disinfectants 11 

heat 9 

light 11 

moisture 9 

chemical  reaction  necessary  for 10 

classification  of,  found  in  milk 94 

common  forms  of,  in  cows'  milk 80 

content  of  milk,  influence  of  season  on 92 

weather  on 87 

culture  method  of  investigation  of 14,  18 

definition  of 2 

distribution  of 4 

in  centrifugal  process 183 

in  butter 244 

centrifuge-slime 184 

cheese 267 

279 


280  INDEX. 

PAGE 

Bacteria,  in  cream 184 

ice 133 

milk 83,  184 

rennet  extract 263 

skim-milk 184 

soil , 129 

water 131 

increase  of,  in  milk 88 

injurious  to  milk 100 

kinds,  not  numbers,  of  most  importance 90 

lactic  acid,  forms  of 229 

microscopic  examination  of 13 

multiplication  of,  by  division 5 

spores 6 

non-pathogenic  forms  of 7 

number  of,  in  milk 83 

pathogenic  forms  of 7 

producing  lactic  fermentation 100,  229 

butyric  fermentation % 101 

putrefactive 104 

size  of 4 

weight  of 4 

Bacteriological  methods  of  investigations 12 

Bacteriology,  literature  of 12 

Bedding,  importance  of. 29 

Bovine  tuberculosis,  American  literature  of , 46 

precautions  in  cases  of 49 

Butter 204 

bacteriain 244 

canning  of •"••. 250 

diseases  of 252 

from  extractor 248 

radiator 248 

sour  cream 207 

sweet  cream , . .  .  , 205 

influence  of  air  and  light  on ,  239 

manufacture  and  handling  of 237 

preservation  of 249 

salting  of 241 

transportation  of 247 


INDEX.  281 

PAGE 

Butter,  use  of  chemicals  in  preserving 249 

working  of 240 

Butyric  fermentation,  bacteria  producing 101 

Canning  of  butter 250 

Centrifugal  process  of  cream  separation.   181 

distribution  of  bacteria  in 183 

Cheese 258 

curing  of 265 

gases  in  holes  of 264 

making,  bacteria  and. 259 

literature  on 259 

literature  on 277 

new-method  274 

old-method 270 

methods  of  manufacture 261,  262,  267 

number  of  bacteria  in „ 267 

Chemicals,  use  of,  for  preserving  butter 249 

milk 144 

Classification  of  bacteria  found  in  milk 94 

Clean  hands,  necessity  of,  in  factory  work 110 

Cleaning  of  cows,  importance  of 36 

Cleanliness  in  butter  and  cheese  factories  108 

milker.   39 

Clothes  of  factory  hands ; 109 

change  of 109 

Coccus  forms  of  bacteria,  definition  of 2 

Condensed  milk ...   146 

Cow  stables,  light  in 50 

stalls     34 

Cows,  proper  time  of  feeding 53 

Cream 166 

cooling  of 190 

from  centrifuges 181 

gravity  methods . , . . .  166 

pasteurization  of 215 

ripening  of : 190 

by  acid  starters 215 

pure  cultures * 220 

latest  investigations  regarding  233 


282  INDEX. 

PAGE 

Cream,  ripening-room  and  vessels  for 214 

separation,  shallow  setting  system  of 166 

modern  gravity  systems  of 175 

centrifugal  system  of 181 

treatment  of,  previous  to  churning 204 

Creamery  walls  and  ceilings 118 

Creameries,  use  of  water  in Ill 

Dahl's  method  of  milk  sterilization 154 

Delay  in  centrifuging  milk,  loss  from 59 

removing  milk  from  stable 58 

setting  milk,  loss  from 59 

Disinfectants  for  use  in  factories 126 

stable 76 

Disinfection  of  butter  and  cheese  factories 125 

stable    76 

Duelund,  milk  and  butter  disease  at , 20 

Engli-Sinclair  method  of  milk-sterilization 161 

Extractor  butter 248 

Factories,  admittance  to 108 

cleanliness  in 108 

disinfection  of 125 

drainage  from 121 

location  of 123 

surroundings    * 121 

use  of  purified  water  in 136 

water  in Ill 

ventilation  of 119 

Factory  floor 114 

hands,  clothes  of. 109 

odor,  cause  of Ill 

purposes,  water  for 127 

Farm  dairy,  the 124 

Floor  in  butter  and  cheese  factories 114 

Fermenting  foods,  dangers  of  infection  from 55 


Grain-raising,  relation  of,  to  cleanliness  in  stable. 


INDEX.  283 

PAGE 

Ice,  bacteria  in 133 

value  of,  to  the  dairyman 66 

Impurities  in  milk 31 

Infection  of  milk  during  milking 28 

in  stable,  prevention  of 26 

precautions  against 28 

sources  of,  in  stable 26 

Inflammation  of  the  udder,  milk  of  cows  suffering  from 47 

Introductory 1 

Lactic  acid  bacteria,  forms  of 229 

fermentation,  bacteria  causing 100 

Microscopic  examination  of  bacteria 13 

Milk,  abnormal 44 

aeration  of « 63 

amphoteric  reaction  of 45 

as  drawn  from  the  udder 23 

bacteria  in 83 

cans,  arrangement  for  steaming 71 

care  of,  in  private  households .•  •  •  •  141 

condensed- 146 

coolers • 64 

cooling  of 62 

delay  in  removal  of,  from  stable 58 

depots 141 

diseased 50 

for  baby-feeding 159 

city  consumption 137 

sanatoriums 159 

from  cows  suffering  from  inflammation  of  the  udder 47 

tuberculous  cows 45 

hauling  of 62 

impurities  in 31 

increase  in  bacterial  content  of 88 

infection  of,  during  milking 28 

inthestable 26 

micro-organisms  in,  other  than  bacteria 106 

mixing  evening  and  morning 68 

pails,  care  of 68 


284  INDEX. 

PAGE 

Milk,  pasteurization  of 157 

preservation  of,  by  freezing 148 

prevention  of  infection  of,  in  the  stable 26 

sterilization  of,  by  Dahl's  method 154 

Engli-Sinclair's  method 161 

Scherff  s  method 151 

Soxhlet's  method 162 

filtration 148 

heating 150 

straining  of 60 

use  of  chemicals  for  preservation  of 144 

vessels,  steaming  of ...-.- 71 

use  of  soda  in  cleaning 70 

when  to  cool , 66 

Milker,  cleanliness  in  the * 39 

Milker's  hands,  wash-water  for 40 

Milking,  manner  of , 41 

with  wet  hands ,  41 


Paris  butter 205 

Pasteurization  apparatus 198 

of  cream 190 

influence  of,  on  yield  of  butter 212 

water  content  of  butter  212 

milk..... 158 

skim-milk 196 

use  of,  in  creameries.. 212 

Preservation  of  butter 249 

Pure  air,  importance  of 52 

Pure  cultures,  literature  on  the  subject  of 232 

useof,  in  cream  ripening 220 

shallow-setting  system  of  cream-separation  228 
Putrefactive  bacteria 104 

Radiator  butter  248 

Rennet 262 

Rennet  extract,  number  of  bacteria  in 263 

Ripening  process,  methods  of  conducting 215 

room  and  vessels 213 


INDEX.  285 

* 

PAGE 

Sanatoriums,  milk  for 159 

Scherff's  method  of  sterilization  of  milk 151 

Separation  of  cream,  methods  of 166 

Separator  cream 181 

Skim-milk 193 

pasteurization  of 196 

separator,  value  of 202 

Soda,  use  of,  in  cleaning  milk- vessels , 70 

Sour-cream  butter 207 

Soxhlet's  method  of  sterilization  of  milk 162 

Spirillum  forms  of  bacteria,  definition  of 2,  4 

Stable,  cleaning  of,  annual 74 

daily.. 54 

disinfection  of 76 

flooring 33 

whitewashing 75 

Steaming  milk- vessels 71 

Sterilization,  Arnold's  steam  cooker  for 16 

intermittent 15 

of  milk 153 

methods  of ......  16 

of  culture  media 15 

milk 144 

methods  of , 161 

Sweet-cream  butter 205 

Tuberculosis,  bovine,  American  literature  of 49 

precautions  in  cases  of 46 

Tuberculous  cows,  milk  from , 45 

Water  for  factory  purposes 127 

iced,  use  of 132 

purification  of 131 

purified,  uses  of 136 

sterilization  of 132 

Whitewashing  of  stable 75 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 

AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


LD  21-95m-7,'37 


>YB 


47241 


4>3 


3 


(J 


